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THE  FERTILITY  IN  ILLINOIS  SOILS 

BY  CYRIL  G.  HOPKINS,  CHIEF  IN  AGRONOMY  AND  CHEMISTRY,  AND 
JAMES  H.  PETTIT,  ASSISTANT  CHIEF  IN  SOIL  FERTILITY 

"Westward  the  course  of  empire  takes  its  way,"  with  ruined 
lands  behind. 

The  purpose  of  the  six  years'  work  represented  in  this  bulletin 
is  to  furnish  definite  facts  and  necessary  information  to  Illinois 
landowners  and  farmers  that  will  enable  them  to  plan  and  adopt 
systems  of  farming  under  which  the  soils  of  Illinois  will  be  certain 
to  continue,  or  improve,  in  productive  power  instead  of  decreasing 
in  fertility  as  they  are  doing  under  the  most  common  present  prac- 
tices. 

While  the  bulletin  deals  primarily  with  the  invoice  of  plant  food 
in  the  most  important  Illinois  soils  found  in  a  general  soil  survey 
of  the  state,  its  value  is  greatly  increased  and  strengthened  because 
of  the  large  amount  of  definite  information  concerning  the  numerous 
soil  types  already  accumulated  in  connection  with  the  detail  soil 
survey  which  is  being  conducted  under  the  immediate  charge  of 
Professor  J.  G.  Mosier  with  a  corps  of  able  assistants ;  also  by  the 
numerous  results  already  obtained  from  the  soil  experiments  which 
are  carried  on  in  many  parts  of  the  state  on  representative  fields  in 
charge  of  Superintendent  J.  E.  Readhimer  and  his  assistants. 

But  the  absolute  basis  of  these  investigations  rests  upon  chem- 
ical analysis,  and  especial  acknowledgments  are  made  to  the  fol- 
lowing chemists  upon  whose  chemical  knowledge  and  analytical 
skill  the  accuracy  of  the  work  depends :  Professor  I.  O.  Schaub, 
now  at  the  Iowa  Station ;  Doctor  E.  M.  East,  now  at  the  Connecti- 
cut Station ;  Mr.  W.  F.  Pate,  now  at  the  Ohio  Station ;  Mr.  An- 
drew Ystgard,  deceased ;  Mr.  N.  E.  Bell,  now  at  the  Alabama  Sta- 
tion ;  and  Doctor  L.  H.  Smith,  A.  W.  Gregory,  and  E.  VanAlstine, 
who  continue  in  the  service  of  Illinois. 

PLAN  OF  INVESTIGATION 

In  the  investigation  of  the  fertility  of  the  soil  in  its  relation  to 
crop  production  five  general  questions  must  be  considered. 

i.  What  are  the  plant  food  requirements  of  the  crops  to  be 
produced  ? 

187 


188  BULLETIN  No.  123.  [February, 

2.  What  is  the  total  stock  of  plant  food  contained  in  the  soil 
strata  which  we  are  able  to  control? 

3.  How  rapidly  by  practical  methods  can  this  plant  food  be 
made  available  to  the  growing  crops  ? 

4.  When  necessary,  in  order  to  produce  more  profitable  crop 
yields,  how  can  we  most  economically  supplement  or  increase  the 
plant  food  in  the  soil? 

5.  Under  what  systems  will  the  productive  power  of  the  soil  be 
permanently  maintained? 

PLANT  FOOD  REQUIRED  BY  CROPS 

It  should  be  remembered  that  of  the  ten  different  chemical 
elements  required  for  the  growth  of  agricultural  plants,  three  come 
directly  from  air  and  water  in  practically  unlimited  amounts  (except 
in  time  of  drouth),  and  that  these  three,  carbon,  hydrogen,  and  oxy- 
gen, constitute,  as  a  rule  about  95  percent  of  the  mature  crop. 
Nevertheless  each  of  the  seven  elements  obtained  from  the  soil, 
though  aggregating  only  5  percent,  is  just  as  necessary  to  the  life 
and  full  development  of  the  plant,  as  are  these  three. 

The  four  elements,  sulfur,  calcium,  iron,  and  magnesium,  are 
required  by  crops  in  such  small  amounts  and  are  present  in  nearly 
all  soils  in  such  large  amounts  that  the  supply  rarely  if  ever  becomes 
depleted,  thus  narrowing  the  problem  essentially  to  three  elements, 
constituting  not  more  than  4  percent  of  the  average  crop. 

The  productive  capacity  of  practically  all  soils  in  good  physical 
condition  is  measured  by  the  available  supply  of  the  three  plant 
food  elements,  phosphorus,  potassium,  and  nitrogen,  because  they 
are  required  by  all  crops  in  very  considerable  quantities,  while  in 
most  soils  the  supply  of  one  or  more  of  them  is  limited.  If  the 
supply  of  one  of  these  elements  is  too  limited,  it  must  as  a  conse- 
quence, limit  the  yield  of  the  crop,  even  though  all  other  factors  es- 
sential to  crop  production  are  well  provided.  It  is  because  of  these 
facts  that  the  three  elements,  phosphorus,  potassium,  and  nitrogen, 
in  commercial  form,  have  come  to  have  a  recgnized  money  value. 

A  careful  study  of  Table  i  is  sufficient  to  make  the  reader  familiar 
with  the  plant  food  requirements  of  the  more  important  Illinois 
crops.  Information  is  also  given  regarding  the  amounts  of  these 
valuable  elements  contained  in  the  different  parts  of  the  crop,  as 
grain,  stalks,  and  straw,  and  in  some  animal  products,  in  order  that 
it  may  be  known  with  some  degree  of  accuracy  how  much  of  each 
element  is  removed  from  the  soil  in  crops  and  how  much  is  sold 
from  the  farm  in  different  kinds  of  farm  produce.  The  ideal  prac- 
tice is  to  return  to  the  soil  in  farm  manures  all  plant  food  not  sold 
from  the  farm. 


/pa*.] 


THE  FERTILITY  IN  ILLINOIS  SOILS. 


189 


The  data  given  in  Table  I  are  on  the  basis  of  pounds  per  acre 
for  crop  yields  which  are  large,  but  which,  when  the  best  conditions 
are  furnished,  have  been  and  may  be  produced  with  very  great 
profit — yields  that  may  well  stand  as  an  ideal,  desirable  and  possible 
to  be  attained. 

Of  course,  approximately  proportionate  amounts  would  be  re- 
quired for  any  other  yields.  Thus,  if  it  is  preferred  to  plan  to  make 
possible  yields  only  one-half  as  large,  then  the  amounts  given  may 
be  divided  by  two. 

TABLE  1. — FERTILITY  IN  FARM  PRODUCE 
(Approximate  maximum  amounts  removable  per  acre  annually) 


Produce. 

Pounds. 

Market  value. 

Kind. 

Amount. 

Nitro- 
gen. 

Phos- 
phorus. 

Potas- 
sium. 

Nitro- 
gen. 

Phos- 
phorus. 

Potas- 
sium. 

Total 
value. 

Corn,  grain  .  .  . 

100  bu. 

100 

17 

19 

$15.00 

$  2.04 

$  1.14 

$18  18 

Corn  stover  .  .  . 

3T. 

48 

6 

52 

7.20 

.72 

3.12 

11.04 

Corn  crop  ...... 

148 

23 

71 

22.20 

2.76 

4.26 

29.22 

Oats,  grain  .  .  . 

lOObu. 

66 

11 

16 

9.90 

1.32 

.96 

12.18 

Oat  straw  

2^T. 

31 

5 

52 

4.65 

.60 

3  12 

8.37 

Oat  crop  ...... 

97 

16 

68 

14  55 

1  92 

4  08 

20  55 

Wheat,  grain  . 

SO  bu 

71 

12 

13 

10.65 

1.44 

.78 

12.87 

Wheat  straw.  . 

2^T. 

25 

4 

35 

3.75 

.48 

2.10 

6.33 

Wheat  crop  .  .  . 

96 

16 

48 

14.40 

1.92 

2.88 

19.20 

Timothy  hay.  . 

3T. 

72 

9 

71 

10.80 

1.08 

4.26 

16.14 

Clover  seed..  .  . 

4bu. 

7 

2 

3 

1.05 

.24 

.18 

.1.47 

Clover  hay.  .  .  . 

4T. 

160 

20 

120 

24.00 

2.40 

7.20 

33.60 

Cowpea  hay.  .  . 
Alfalfa  hay  

3T. 

8T. 

130 

400 

14 
36 

98 
192 

19.50 
60.00 

1.68 
4.32 

5.88 
11.52 

27.06 
75.84 

Apples  

600  bu. 

47 

5 

57 

7.05 

.60 

3.42 

11.07 

L/eaves  

4T. 

59 

7 

47 

8.85 

.84 

2.82 

12.51 

Wood  growth. 

1/50  tree 

6 

2 

.   5 

.90 

.24 

.30 

1.44 

Total  crop  

112 

14 

109 

16.80 

1.68 

6.54 

25.02 

Potatoes  

300  bu. 

63 

13 

90 

9.45 

1.56 

5.40 

16«41 

Sugar  beets.  .  . 

20  T. 

100 

18 

157 

15.00 

2.16 

9.42 

26.58 

Fat  cattle  

1,000  Ib. 

25 

7 

1 

3.75 

.84 

.06 

4.65 

Fat  hogs  

1,000  Ib. 

18 

3 

1 

2.70 

.36 

.06 

3.12 

Milk  

lO.OOOlb. 

57 

7 

12 

8.55 

.84 

.72 

10.11 

Butter  

500  Ib. 

1 

0.2 

0.1 

.15 

.02 

0.1 

.18 

The  value  of  the  elements  is  computed  on  the  basis  of  the  pres- 
ent market  prices  for  readily  available  plant  food,  namely : 

Nitrogen 15  cents  a  pound 

Phosphorus 12  cents  a  pound 

Potassium 6  cents  a  pound 


190 


BULLETIN  No.  123. 


[February, 


It  may  be  said  that  other  similar  crops  resemble  somewhat 
closely  those  given  in  Table  I  as  to  plant  food  requirements.  Thus 
rye  and  barley  are  not  markedly  different  in  requirements  from 
wheat  and  oats,  considering  equal  yields  in  pounds  of  grain  and 
straw.  Other  root  crops  may  be  compared  with  sugar  beets,  other 
grasses  with  timothy,  hay  from  other  annual  legumes  with  cowpea 
hay,  and  other  biennial  and  perennial  legumes  may  be  compared  in 
a  general  way  with  red  clover  and  alfalfa. 

The  figures  given  in  Table  i  are  based  upon  averages  of  many 
analyses,  of  which  some  have  been  made  by  the  Illinois  Station  and 
others  by  various  chemists  in  America  and  Europe.  These  aver- 
ages are  believed  to  be  trustworthy  for  large  crops  of  good  quality. 
Abnormal  or  special  crops  may  vary  considerably  from  these  aver- 
ages. Thus  we  have  high-protein  corn  and  low-protein  corn,  one 
strain  requiring  nearly  twice  as  much  nitrogen  and  somewhat  more 
phosphorus  than  the  other;  and  we  have  shown  in  Bulletins  76 
and  94  that  alfalfa  and  cowpeas  are  not  only  much  more  productive 
but  much  richer  in  nitrogen  when  grown  on  Illinois  soils  with  the 
proper  bacteria  than  without  bacteria. 

TABLE  2.— FERTILITY  IN  MANURE,  ROUGH  FEEDS,  AND  FERTILIZERS 


Name  of  material. 

Pounds  per  ton. 

Value  per  ton. 

Nitro- 
gen. 

Phos- 
phorus. 

Potas- 
sium. 

Nitro- 
gen. 

Phos- 
phorus. 

Potas- 
sium. 

Total 
value. 

Fresh  farm  manure  

10 

16 
12 
10 

40 
43 
SO 

280 
310 
400 

80 
20 

2 

2 
2 
2 

O 

5 
4 

180 

250 
250 
125 

10 

10 

17 

21 
14 

30 
33 
24 

850 
850 
200 
100 

$1.50 

2.40 
1.80 
1.50 

6.00 
6.45 

7.50 

42.00 
46.50 
60.00 

12.00 
3.00 

$  .24 

.24 
.24 

.24 

.60 
.60 

.48 

18.00 
25.00 
10.00 
15.00 

1.20 

$    .60 

1.02 
1.26 
.84 

1.80 
1.98 
1.44 

51.00 
51.00 
12.00 
6.00 

$2.34 

3.66 

3.30 

2  58 

8.40 
9.03 
9.42 

42.00 
46.50 
60.00 

30.00 
28.00 
10.00 
15.00 

51.00 
51.00 
12.00 
7.20 

Corn  stover  

Oat  straw  

Wheat  straw  

Clover  hay  

Cowpea  hay  

Alfalfa  hay  

Dried  blood  

Sodium  nitrate  

Ammonium  sulf  ate  

Raw  bone  meal  

Steamed  bone  meal  

Raw  rock  phosphate  

Acid  phosphate  

Potassium  chlorid  

Potassium  sulf  ate  

Kainit  

Wood  ashes*  

*Wood  ashes  also  contain  about  1000  pounds  of  lime  (calcium  carbonate) 
per  ton. 


1908.]  THE  FERTILITY  IN  ILLINOIS  SOILS.  191 

SOURCES  OF  PLANT  FOOD 

If  the  productive  capacity  of  Illinois  soils  is  to  be  maintained 
elements  of  plant  food  which  are  present  in  such  small  amounts  as 
to  limit  crop  yields  even  under  good  systems  of  farming  must  be 
returned  to  the  soil  as  needed,  and  information  is  given  in  Table  2 
to  show  the  average  quantities  in  pounds  of  the  different  valuable 
elements  of  plant  food  contained  in  one  ton  of  average  fresh  farm 
manure,  rough  feeds  and  bedding,  and  other  fertilizer  materials. 

In  computing  the  value  of  the  plant  food  in  these  materials, 
nitrogen  is  counted  at  15  cents  a  pound  and  potassium  at  6  cents  a 
pound;  while  phosphorus  is  counted  at  4  cents  a  pound  in  raw 
rock  phosphate,  at  10  cents  a  pound  in  bone  meal,  and  at  12  cents 
a  pound  in  acid  phosphate,  these  prices  being  based  upon  average 
market  values  for  the  standard  fertilizing  materials  in  small  lots. 
In  carload  lots  lower  prices  may  be  secured. 

The  information  contained  in  Table  i  and  Table  2  will  be  found 
of  value  in  connection  with  a  study  of  the  composition  of  Illinois 
soils  shown  in  Table  3,  especially  in  planning  systems  for  the  im- 
provement and  permanent  maintenance  of  the  different  types  of  soil, 
containing  varying  amounts  of  these  plant  food  elements. 

Thus,  it  should  be  plain  to  see  that  to  supply  the  plant  food  for 
a  four-year  rotation  consisting  of  corn  for  two  years,  followed  by 
oats  with  clover  seeding  the  third  year,  and  clover  hay  and  seed 
crops  the  fourth  year,  assuming  the  yields  given  in  Table  I,  would 
require  an  application  of  39  tons  of  manure  to  supply  the  nitrogen, 
41  tons  to  supply  the  phosphorus,  or  33  tons  to  supply  the  potas- 
sium, assuming  that  the  clover  secures  from  the  air  sufficient  nitro- 
gen for  the  clover  crops  removed.  In  making  computations  of  this 
sort  it  is  safe  to  assume  that  the  clover  takes  at  least  as  much  nitro- 
gen from  good  soil  as  remains  in  the  clover  roots  and  stubble.  It 
should  also  be  understood  that  there  will  be  a  very  considerable 
loss  of  nitrogen  in  drainage  waters,  which  may  easily  amount  to 
one-third  of  the  nitrogen  applied  if  the  land  is  much  exposed  with- 
out cover  crops. 

It  should  be  kept  in  mind  that  it  becomes  much  easier  to  main- 
tain the  supply  of  nitrogen  if  some  clover  is  plowed  under  and  if 
the  rotation  is  extended  to  include  two  or  three  years  of  pasture 
with  a  mixture  of  legumes  and  grasses,  as  red  clover,  alsike,  alfalfa, 
timothy,  and  red  top.  If  the  supply  of  manure  is  sufficient  to  fur- 
nish only  12  tons  of  manure  per 'acre  once  in  four  years,  it  may  still 
be  possible  to  maintain  the  supply  of  nitrogen  and  humus  by  sup- 
plementing the  manure  with  legume  crops  and  catch  crops  grown  in 
the  rotation  and  in  pasture,  but  in  such  case  it  is  plain  to  see  that 


192  BULLETIN  No.  123.  [February, 

while  the  crops  remove  82  pounds  of  phosphorus  from  an  acre  the 
12  tons  of  manure  return  only  24  pounds  of  that  element,  leaving 
a  deficiency  of  58  pounds,  which,  however,  can  be  made  up  by  apply- 
ing with  the  manure  a  few  hundred  pounds  of  raw  rock  phosphate, 
about  50  pounds  of  phosphate  with  each  load  of  manure  being 
ample  to  maintain  the  phosphorus  content  of  the  soil,  larger  amounts 
being  used  if  it  is  desired  gradually  to  increase  the  supply  of  phos- 
phorus in  the  soil.  It  will  be  observed  that  one  ton  of  rock  phos- 
phate contains  more  phosphorus  than  100  tons  of  average  fresh 
farm  manure. 

If  the  soil  is  exceedingly  rich  in  .potassium,  as  it  will  be  shown 
is  the  case  with  most  Illinois  soils,  then  no  further  consideration 
need  be  given  to  that  element,  except  to  insure  its  liberation  by  the 
action  of  decaying  organic  matter,  the  supply  of  which  will  be 
maintained  by  following  the  suggestions  for  maintaining  the  sup- 
ply of  nitrogen.  On  the  other  hand  with  soils  exceedingly  deficient 
in  potassium,  as  with  certain  peaty  swamp  lands  whose  composi- 
tion is  shown  in  Table  3,  that  element  may  well  be  supplied  in  some 
concentrated  potassium  salt,  such  as  potassium  chlorid  (sometimes 
incorrectly  called  "muriate  of  potash"),  one  ton  of  which  contains 
as  much  potassium  as  85  tons  of  average  fresh  farm  manure. 

If  the  soil  is  markedly  sour,  or  acid,  of  course  the  acidity  should 
be  corrected  with  an  application  of  some  form  of  lime,  ground 
limestone  being  the  most  economical  and  satisfactory  form  to  use 
as  a  rule. 

In  case  the  total  supply  of  potassium  in  the  soil  is  very  large 
but  the  supply  of  decaying  organic  matter  so  small  .that  applica- 
tions of  soluble  potassium  salts  produce  marked  increase  in  crop 
yields,  as  shown,  for  example,  on  the  prairie  lands  of  southern  Illi- 
nois described  in  the  following  pages,  it  should  be  understood  that 
the  effect  is  produced  not  entirely  by  the  element  potassium  but  in 
part  at  least  by  the  stimulating  action  of  the  soluble  salt,  and  that 
instead  of  using  a  high-priced  concentrated  potassium  salt,  as  would 
be  best  to  supply  potassium  for  peaty  swamp  land,  it  will  be  les.s 
expensive  and  more  profitable  to  use  on  southern  Illinois  soil  such 
a  low-priced  mixture  of  soluble  salts  as  kainit,  which  contains  nearly 
25  percent  of  potassium  sulfate,  about  16  percent  of  magnesium 
sulfate,  12  percent  of  magnesium  chlorid,  and  33  percent  of  sodium 
chlorid  (common  salt),  together  with  about  14  percent  of  combined 
water. 

For  more  complete  discussion  of  the  use  of  limestone,  Illinois 
readers  are  referred  to  Circular  no,  "Ground  Limestone  for  Acid 
Soils." 


THE  FERTILITY  IN  ILLINOIS  SOILS.  193 

ILLINOIS  SOIL  AREAS  AND  SOIL  TYPES 

According  to  geological  investigation  there  have  been  at  least 
three  different  periods  when  glaciers,  or  ice  sheets,  have  covered 
more  or  less  of  the  State  of  Illinois,  in  consequence  of  which  nearly 
all  of  the  surface  of  the  state  has  been  covered  with  drift,  or  glacial 
material,  which  is  termed  till,  or  bowlder  clay,  and  is  characterized 
by  the  presence  of  more  or  less  coarse  material  varying  in  size  from 
pebbles  to  bowlders,  imbedded  in  clay,  the  materials  having  been 
gathered  by  the  ice  sheets  as  they  slowly  flowed  over  the  surface  of 
the  earth.  In  the  process  of  transportation  much  of  the  drift  became 
finely  ground  so  that  when  finally  deposited  the  till  consisted  of 
material  varying  in  size  from  clay  to  bowlders.  Where  for  a  long 
period  of  time  the  forward  movement  of  the  glacier  was  practically 
equalled  by  the  rapidity  with  which  the  ice  melted,  much  material 
was  deposited,  forming  what  are  termed  moraines,  or  glacial  ridges, 
varying  in  width  from  less  than  a  mile  to  several  miles,  and  extend- 
ing around  the  lobe  of  the  glaciated  area  sometimes  for  a  distance 
of  a  hundred  miles  or  more. 

Generally  the  glacial  till  was  covered  finally  by  a  layer  of  loess, 
which  is  a  fine  material  that  was  transported  by  the  action  of  wind 
or  flowing  water,  probably  from  deposits  of  exposed  till  before  it 
was  protected  by  vegetation  (and  to  some  extent  from  the  melting 
or  evaporating  glaciers),  and  deposited  over  the  state  to  an  average 
depth  of  three  feet  or  less  in  some  areas  (as  in  the  Late  Wisconsin 
glaciation),  and  to  eight  or  ten  feet  in  others  (as  in  the  Upper  Illi- 
noisan  and  -  Pre-Iowan  glaciations)  ;  while  in  the  "Deep  Loess" 
areas  covering  the  bluff  lands  along  some  of  the  large  streams  the 
depth  of  the  loessial  material  may  be  from  twenty  to  one  hun- 
dred feet. 

The  accompanying  general  survey  soil  map  shows  the  areas  that 
have  been  covered  by  the  different  glaciers,  also  the  Unglaciated  and 
Deep  Loess  areas  and  the  general  distribution  of  the  early  and  late 
bottom  lands  and  swamp  areas,  in  which  the  soils  vary  from  heavy 
clays  or  clay  loams  to  peat  beds  on  the  one  hand  or  to  sand  plains 
or  drifting  dunes  on  the  other. 

The  first  glacier  may  have  covered  all  of  Illinois  as  far  south 
as  the  Ozark  Hills  (near  the  south  line  of  Williamson  county)  ex- 
cepting a  part  of  Pike  and  Calhoun  counties  and  an  elevated  area  in 
the  northwest  corner  of  the  state.  The  area  where  the  drift  from 
this  first  glacier  has  not  been  covered  by  a  subsequent  glacier  is 
called  the  Illinoisan  glaciation.  For  our  purpose  we  divide  this  Illi- 
noisan  glaciation  into  three  areas  because  of  difference  in  the  agri- 
cultural values  and  properties  of  the  most  common  soils  in  these 


194  BULLETIN  No.  123.  [Februiry, 

sections  (especially  marked  between  the  Lower  and  Middle  Illi- 
noisan  glaciations).  These  three  areas  we  call  the  Lower  Illinoisan 
glaciation  (No.  3),  the  Middle  Illinoisan  glaciation  (No.  4),  and  the 
Upper  Illinoisan  glaciation  (No.  5),  each  of  which  will  be  more 
fully  described  later. 

The  second  glacier  extended  only  over  three  or  four  tiers  of 
counties  from  the  north  line  of  the  state,  not  including  JoDaviess 
county.  On  the  area  where  the  drift  from  this  second  glacier  has 
not  been  covered  by  a  later  glacier  we  have  accepted  the  two  divi- 
sions *recognized  by  geologists,  one  of  which  (No.  6)  we  call  the 
Pre-Iowan  glaciation,  and  the  other  (No.  7)  the  lowan  glaciation. 

The  third  and  last  glacier  covered  approximately  the  northeast 
one-quarter  part  of  the  state,  and  this  area  is  called  the  Wisconsin 
glaciation.  This  is  divided  into  two  areas,  the  early  Wisconsin 
glaciation  (Nos.  9  and  n)  and  the  late  Wisconsin  glaciation  (Nos. 
10  and  12). 

According  to  formation  we  recognize  fourteen  large  soil  areas 
in  the  state,  although  some  formations  are  scattered  in  separated 
tracts  and  each  of  the  fourteen  areas  may  contain  several  or  many 
different  types  of  soil. 

In  studying  soil  types  we  consider  the  time  and  method  of 
formation;  the  topography  as  affecting  surface  drainage  and  sur- 
face washing;  the  texture,  varying  from  light,  loose,  or  friable  to 
heavy,  compact,  or  plastic;  the  structure,  especially  with  reference 
to  uniformity  or  differences  of  the  soil  strata  at  different  depths; 
and  we  also  recognize,  of  course,  the  different  materials  of  which 
soils  are  composed,  as  organic  matter,  clay,  silt,  sand,  gravel,  and 
stone.  In  naming  a  soil  type  we  try  to  indicate  ( I )  the  great  soil 
area  in  which  it  is  found  (2)  the  color  of  the  soil,  (3)  the  chief 
material  of  which  it  is  composed  (as  clay,  silt,  sand,  etc.)  and  some- 
times (4)  the  topography.  Sometimes  the  name  also  indicates  the 
character  of  the  subsoil,  especially  if  it  is  unusual  or  abnormal. 

We  use  the  term  clay  to  designate  only  true  plastic  clay,  and  not 
as  it  is  so  commonly,  though  incorrectly,  used  to  describe  almost  any 
fine-grained  soil  or  subsoil  that  is  deficient  in  organic  matter.  True 
clay  is  like  dough,  being  sticky  or  plastic  and  without  individual 
particles  distinguishable  by  the  naked  eye. 

By  the  term  silt  is  meant  a  grade  of  soil  particles  finer  than  sand, 
too  fine  to  feel  the  individual  grains  with  the  fingers,  but  yet  granu- 
lar to  the  eye  and  not  sticky  or  plastic  when  free  from  clay.  Silt  is 

*These  divisions  are  grouped  together  for  the  sake  of  simplicity,  although 
the  terms  Pre-Iowan  and  lowan  recognize  a  greater  difference  in  time  of  forma- 
tion ~than  the  terms  Early  lowan  and  Late  lowan  which  have  been  used  ten- 
tatively. 


I9o8.]  THE  FERTILITY  IN  ILLINOIS  SOILS.  195 

by  far  the  most  common  material  in  our  ordinary  prairie  and  timber 
soils  and  subsoils,  although  such  soils  also  contain  some  smaller 
percentages  of  sand  and  clay. 

In  Table  3  is  given  the  average  composition  in  pounds  per  acre 
of  the  surface  soil,  approximately  7  inches  deep  (more  exactly  6^3 
inches)  of  the  most  important  soil  types  in  the  great  soil  areas  of 
Illinois.  These  data  are  the  average  results  of  analyses  of  many 
representative  samples  of  soil  from  each  soil  type  numbered  and 
named  in  the  table.  The  last  two  figures  in  the  official  number  des- 
ignate the  soil  type  and  the  preceding  figure  (or  figures)  the  area 
in  which  it  is  found  in  accordance  with  the  numbers  on  the  soil  map 
of  Illinois,  except  that  No.  n  may  be  used  for  both  9  and  n,  and 
No.  10  may  be  used  for  both  10  and  12,  because  the  same  soil  types 
are  not  uncommonly  found  on  both  moraines  and  plains.  For  a 
more  complete  outline  of  the  classification  of  the  soils  of  Illinois,  the 
reader  is  referred  to  the  appendix. 

THE  MEANING  OE  SOIL,  ANALYSIS 

In  studying  the  composition  of  different  soils  it  is  well  to  keep 
in  mind  that  our  most  productive  soils  of  normal  physical  composi- 
tion contain  in  the  surface  seven  inches  per  acre  about  8000  pounds 
of  total  nitrogen,  2000  pounds  of  total  phosphorus,  and  above  30,- 
ooo  pounds  of  total  potassium. 

The  total  nitrogen  varies  from  about  2000  pounds  in  the  yellow 
silt  loam  of  the  hill  lands,  or  from  less  than  1500  pounds  in  the 
sand  soil,  to  8900  pounds  in  the  black  clay  loam  prairie  of  the  Late 
Wisconsin  glaciation  and  even  to  nearly  35,000  pounds  in  the  peaty 
swamp  soil. 

The  total  phosphorus  varies  from  about  800  pounds  in  the  gray 
silt  loam  prairie  of  southern  Illinois  to  about  2000  pounds  as  an 
average  of  the  richest  areas  of  black  clay  loam;  while  the  total 
potassium  varies  from  3000  pounds  in  the  peaty  swamp  soil  to  48,- 
ooo  in  the  Late  Wisconsin  yellow-gray  silt  loam. 

For  convenient  study  and  ready  comparison  the  twenty-five 
soils,  comprising  the  most  extensive  and  important  types  in  the 
great  soil  areas,  are  arranged  in  the  tables  in  five  groups. 

First,  the  group  of  undulating  prairie  lands,  varying  in  topog- 
raphy from  level  to  rolling,  and  including  the  somewhat  peculiar 
gray  silt  loam  on  tight  clay  of  the  Lower  Illinoisan  glaciation  in  the 
Illinois  wheat  belt  and  the  ordinary  brown  silt  loam  soils  of  the 
corn  belt  found  in  the  six  other  glacial  areas,  and  especially  exten- 
sive in  the  Middle  and  Upper  Illinoisan  and  in  the  Early  Wisconsin 
glaciations,  constituting  by  far  the  most  common  corn  belt  soils. 


196 


BUU.ETIN  No.  123. 


[February, 


TABI,E  3. — FERTILITY  IN  ILLINOIS  Soii,s 
Average  Pounds  per  Acre  in  Surface  Soil  (0-7  inches)* 


Soil 
tTpe 
No. 

Soil  area  or 
glaciation. 

Soil  type. 

Total 
nitro- 
gen. 

Total 
phos- 
phorus. 

Total 
potas- 
sium. 

Limestone 
required. 

Prairie  lands,  undulating. 


330 

Lower  Illinoisan. 

Gray  silt  loam  on 
tight  clay  

2880 

840 

24940 

2  to  5  tons 

426 

Middle  Illinoisan 

Brown  silt  loam  

4370 

1170 

32240 

Rarely 

526 

Upper  Illinoisan.. 

Brown  silt  loam  ...... 

4840 

1200 

32940 

Rarely 

626 

Pre-Iowan  .    .  . 

Brown  silt  loam  

4290 

1190 

35340 

Yz  to  1  ton 

726 

lowan  

4910 

1220 

32960 

^  to  1  ton 

1126 

Early  Wisconsin. 

Brown  silt  loam  

5050 

1190 

36250 

Rarely 

1026 

Late  Wisconsin.  . 

Brown  silt  loam  

6750 

1410 

45020 

Rarely 

Prairie  lands,  flat. 


420 

Middle  Illinoisan 

Black  clay  loam'  

5410 

1430 

31860 

None 

520 

Upper  Illinoisan.. 

Black  clay  loam  

6760 

1690 

29670 

None 

1120 

Early  Wisconsin. 

Black  clay  loam  

7840 

2030 

35140 

None 

1220 

Late  Wisconsin.  . 

Black  clay  loam  .  . 

8900 

1870 

37370 

None 

Timber  uplands,  rolling  or  hilly. 


135 

Un  glaciated.. 

Yellow  silt  loam  

1890 

950 

31450 

2  to  5  tons 

335 

Lower  Illinoisan 

Yellow  silt  loam  ...    . 

2150 

950 

31850 

2  to  5  tons 

435 

Middle  Illinoisan 

Yellow  silt  loam  

1870 

820 

33470 

1  to  2  tons 

535 

Upper  Illinoisan.. 

Yellow  silt  loam  

2010 

840 

34860 

1  to  2  tons 

635 

Pre-Iowan  

Yellow  silt  loam  

2390 

850 

37180 

1  to  2  tons 

35 

Yellow  silt  loam  

1910 

910 

35780 

1  to  2  tons 

1135 

Early  Wisconsin  . 

Yellow  silt  loam  

1890 

870 

32720 

1  to  2  tons 

864 

Deep  loess  

Yellow  fine  sandy 

loam  

2170 

960 

35640 

1  to  2  tons 

Timber  uplands,  undulating. 


1034 
760 

Late  Wisconsin.  . 
lowan  

Yellow-gray  silt  loam 
Brown  sandy  loam  .  .  . 

2890 
3070 

810 
850 

47600 
26700 

(?) 
(?) 

Sand,  swamp,  and  bottom  lands. 


1331 
1451 
1481 

1401 

Old  bottom  lands. 
Late  bottom  lands 
Sand  plains  and 
dunes  

Deep  gray  silt  loam  .  . 
Brown  loam  

3620 
4720 

1440 
34880 

1420 
1620 

820 
1960 

36360 
39970 

30880 
2930 

1  to  4  tons 
Rarely 

(?) 
Rarely 

Sand  soil  

Late  swamp  

Deep  peat  

*The  numbers  given  in  Table  3  represent  the  total  amounts  contained  in 
two  million  pounds  of  the  surface  soil  on  the  dry  basis,  with  the  exception  of 
peaty  swamp  soil,  for  which  the  amounts  in  one  million  pounds  are  used,  be- 
cause its  specific  gravity  is  only  one-half  that  of  ordinary  soil,  and  of  sand  soil 
for  which  2^2  million  pounds  are  used,  because  it  is  about  one-fourth  heavier 
than  ordinary  soil. 


THE  FERTILITY  IN  ILLINOIS  SOILS.  197 

Second,  the  heavy  black  clay  loam  soils  found  in  the  very  flat 
prairies,  usually  swampy  before  being  drained,  common  in  the  Early 
Wisconsin  and  less  common  in  the  Middle  and  Upper  Illinoisan  and 
in  the  Late  Wisconsin  glaciation. 

Third,  the  eroded  yellow  silt  loams  on  sloping  hillsides,  the  com- 
monest soil  type  in  the  unglaciated  area  and  also  found  on  the  bro- 
ken lands  adjoining  water  courses  in  most  parts  of  the  state;  also 
the  yellow  fine  sandy  loam  of  the  deep  loess  area,  especially  common 
on  the  bluffs  adjoining  the  Mississippi  and  in  places  along  other 
large  streams. 

Fourth,  the  undulating  timber  uplands  of  which  only  the  yel- 
low-gray silt  loam  of  the  Late  Wisconsin  and  the  brown  sandy  loam 
of  the  lowan  glaciation  are  discussed  in  this  bulletin,  these  being 
extensive  and  consequently  of  special  importance  in  those  areas. 

Fifth,  the  sand,  swamp,  and  bottom  land  areas,  which  are  dis- 
cussed only  with  reference  to  sand  soil,  peaty  soil,  and  very  com- 
mon bottom  lands. 

In  both  nitrogen  and  phosphorus  the  black  clay  loam  which 
occupies  the  very  flat  prairie  land  in  the  northeast  quarter  part  of 
Illinois  is  about  two  and  one-half  times  as  rich  as  the  very  extensive 
gray  silt  loam  prairie  land  of  the  Lower  Illinoisan  glaciation. 

In  total  potassium  all  of  the  soils  of  Illinois  are  extremely  rich 
excepting  the  peaty  swamp  soil  and  this  is  extremely  poor  in  this 
element  containing  less  than  one-tenth  as  much  potassium  as  is 
found  in  normal  fertile  soils. 

Even  the  sand  soils  are  rich  in  total  potassium,  showing  that 
much  of  the  material  is  of  granitic  origin. 

While  the  amount  of  plant  food  contained  in  the  soil  at  depths 
below  seven  inches  is  of  interest  and  will  be  found  reported  and  dis- 
cussed in  the  following  pages,  it  should  be  kept  in  mind  that  the 
thing  of  chief  concern  and  importance  in  systems  of  permanent 
profitable  agriculture  is  to  have  and  to  maintain  a  good  surface  soil, 
for  even  a  rich  subsoil  is  of  but  little  value  if  it  lies  beneath  a  worn- 
out  surface.  We  know  that  we  add  manure  and  fertilizers  to  the 
plowed  soil  only  and  that  by  thus  enriching  the  surface  stratum  we 
are  able  to  increase  markedly  the  crop  yields.  These  well  known 
facts  plainly  emphasize  the  importance  of  maintaining  a  rich  sur- 
face soil  at  least  6  or  8  inches  deep. 

The  downward  movement  of  mineral  plant  food  is  very  slight. 
Even  soluble  phosphates  and  potassium  salts  applied  to  the  surface 
and  harrowed  in  do  not  produce  nearly  so  good  results  as  when 
they  are  plowed  down,  thus  putting  them  where  the  plant  roots  feed, 
which  is  chiefly  below  the  first  two  or  three  inches. 


198  BULLETIN  No.  123.  [February, 

A  direct  comparison  of  Table  i  and  Table  3  is  instructive  and 
profitable. 

It  will  be  found,  for  example,  that  a  hundred-bushel  crop  of  corn 
removes  from  the  soil  148  pounds  of  nitrogen,  17  pounds  of  phos- 
phorus, and  19  pounds  of  potassium,  assuming  that  the  corn  is  har- 
vested and  the  stalks  are  burned,  which  is  still  the  most  common 
practice  in  the  Illinois  corn  belt.  In  the  commonest  corn  belt  land, 
the  brown  silt  loams,  there  are  as  a  general  average  (excluding  the 
Late  Wisconsin  glaciation)  about  4800  pounds  of  nitrogen,  1200 
pounds  of  phosphorus,  and  34,000  pounds  of  potassium.  These 
amounts  are  sufficient  to  supply  the  nitrogen  for  such  crops  for  32 
years,  the  phosphorus  for  70  years,  and  the  potassium  for  1790 
years. 

Even  the  total  nitrogen  to  a  depth  of  40  inches  would  extend 
the  possible  time  limit  for  such  crops  to  only  95  years  for  our  most 
common  Illinois  corn  belt  land.  It  will  be  kept  in  mind  of  course 
that  there  is  an  inexhaustible  supply  of  nitrogen  in  the  air  which 
can  be  drawn  upon  by  means  of  legume  crops  with  their  nitrogen- 
fixing  bacteria,  but  from  Table  i  it  will  be  seen  that  a  ton  of  clover 
contains  only  40  pounds  of  nitrogen,  and  it  may  be  well  to  state 
here,  and  well  for  the  reader  to  keep  in  mind  hereafter,  that  the 
nitrogen  contained  in  the  clover  roots  will  not  exceed  one-half  of 
the  amount  contained  in  the  total  growth  above  ground.  Thus  to 
return  the  nitrogen  removed  by  a  hundred-bushel  crop  of  corn 
would  require  a  crop  of  clover  amounting  to  two  and  one-half  tons 
of  hay  together  with  the  corresponding  one  and  one-fourth  ton  of 
roots.  In  addition  to  this  we  must  face  the  fact  that  not  all  of  the 
nitrogen  contained  in  the  clover  plant  is  taken  from  the  air  and  that 
the  loss  of  nitrogen  by  drainage  is  greater  than  the  amount  added 
in  rain.* 

It  is  a  fact,  however,  that  either  by  plowing  under  clover  and 
other  green  manures  and  crop  residues,  or  by  more  or  less  pastur- 
ing and  by  feeding  the  larger  part  of  the  crops  grown  and  saving 
and  returning  all  manure  produced,  the  supply  of  nitrogen  in  the 
soil  can  be  maintained  or  even  increased. 

If  now  we  consider  the  element  phosphorus  we  find  that  the  total 
amount  contained  in  the  plowed  soil  of  the  commonest  Illinois  corn 
belt  land  is  equivalent  to  the  requirement  of  a  hundred-bushel  crop 
of  corn  each  year  for  only  70  years  if  only  the  grain  is  harvested,  or 
but  52  years  if  the  grain  and  stalks  were  both  removed.  In  the 
case  of  phosphorus  instead  of  getting  some  permanent  relief  by 

*Some  nitrogen  may  be  supplied  by  the  soil  bacteria  (azotobacter)  that  fix 
atmospheric  nitrogen  independent  of  legumes,  but  no  estimate  of  the  amount 
can  be  made  because  of  insufficient  data. 


THE  FERTILITY  IN  ILLINOIS  SOILS.  199 

growing  clover  we  only  hasten  the  depletion,  for,  as  will  be  seen 
from  Table  i,  a  four-ton  crop  of  clover  removes  more  phosphorus 
from  the  soil  than  is  contained  in  100  bushels  of  corn. 

In  Table  2  information  is  given  showing  the  amounts  of  phos- 
phorus contained  in  various  materials  that  can  be  applied  to  the  soil. 

If  we  consider  the  element  potassium  we  find  that  the  average 
amount  contained  in  the  surface  soil  of  the  corn  belt  is  sufficient  to 
meet  the  needs  of  100  bushels  of  corn  per  acre  every  year  for  eight- 
een centuries.  Nevertheless  the  liberation  of  sufficient  potassium 
and  possibly  of  other  elements,  as  sulfur,  calcium,  iron,  or  mag- 
nesium, even  though  the  relative  supply  in  the  soil  exceeds  that  of 
potassium,  may  become  a  very  serious  problem,  and  indeed  already 
is  a  serious  problem  in  soils  which  are  deficient  in  decaying  organic 
matter,  as  will  be  more  fully  explained  in  the  discussion  of  specific 
soil  types  (see  Lower  Illinoisan  gray  silt  loam  prairie,  No  330). 

It  should  be  kept  in  mind  that  while  nitrogen  is  ever  present  in 
the  air  in  inexhaustible  quantity,  the  atmosphere  does  not  contain 
phosphorus  or  potassium,  and  the  only  method  of  enriching  the  soil 
in  either  of  those  elements  is  by  direct  application  to  the  land  either 
in  farm  manure  or  other  fertilizers. 

In  Tables  4  and  5  are  given  the  amounts  of  plant  food  contained 
in  the  subsurface  (*7-2O  inches)  and  subsoil  (2040  inches)  of  these 
most  extensive  and  important  Illinois  soil  types.  Except  as  previ- 
ously explained  the  data  given  in  Tables  3,  4,  and  5  represent  the 
amounts  of  plant  food  contained  in  two  million  pounds  of  surface 
soil,  in  four  million  pounds  of  subsurface  soil,  and  in  six  million 
pounds  of  subsoil,  an  acre-inch  of  our  ordinary  silt  loam  and  clay 
loam  soils  weighing  about  300,000  pounds,  dry  basis. 

All  results  are  reported  on  the  basis  of  pounds  per  acre,  because 
the  acre  is  the  unit  of  measure  on  the  farm.  Crops  are  harvested 
and  reported  in  yield  per  acre ;  the  plant  food  removed  is  computed 
in  pounds  per  acre;  manures  or  fertilizers  are  applied  in  tons  or 
pounds  per  acre;  and  in  harmony  with  this  practical  system  the 
composition  of  Illinois  soils  is  reported  and  discussed  also  on  the 
acre  basis.t  On  this  basis  the  stock  of  plant  food  in  the  soil  is 
easily  compared  directly  with  the  plant  food  removed  in  crops  and 
applied  in  manures  or  fertilizers,  and  comparison  between  soil  types 
or  soil  strata  is  also  readily  made. 


*More  exactly  from  62/z  to  20  inches. 

fTo  convert  the  data  to  the  percentage  basis  divide  by  2,  4,  6,  according  to 
the  stratum,  except  that  i,  2,  and  3  should  be  used  for  peat,  and  2l/2,  5,  and  754 
for  sand,  with  proper  placing  of  the  decimal  point  in  all  cases. 


200 


BULLETIN  No.  123. 


[February, 


TABLE  4.— FERTILITY  IN  ILLINOIS  SOILS 
Average  Pounds  per  Acre  in  Subsurface  Soil  (7-20  inches) 


Soil 
type 
No. 

Soil  area  or 
glaciation. 

Soil  type. 

Total 
nitro- 
gen. 

Total 
phos- 
phorus. 

Total 
potas- 
sium. 

Prairie  lands,  undulating. 


330 

Gray  silt  loam  on   tight 

3210 

1500 

53570 

426 

Middle  Illinoisan  

Brown  silt  loam.  .•  

5800 

1920 

62590 

526 

Upper  Illinoisan  

Brown  silt  loam  

6480 

2090 

64820 

626 

Pre-Iowan  

Brown  silt  loam  

4650 

2060 

72370 

726 

lowan  

Brown  silt  loam  

5140 

1940 

66220 

1126 

Brown  silt  loam  

6560 

2000 

72780 

1026 

Late  Wisconsin  .  . 

Brown  silt  loam.  . 

6870 

1960 

96420 

Prairie  lands,  flat. 


420 

Middle  Illinoisan  

6180 

2260 

64070 

520 

Black  clay  loam  

7380 

2690 

60760 

1120 

Early  Wisconsin  

Black  clay  loam  

7200 

3090 

71670 

1220 

Late  Wisconsin  .  . 

Black  clay  loam.  . 

9100 

2860 

78840 

Timber  uplands,  rolling  or  hilly. 


135 

2030 

2120 

67320 

335 

Lower  Illinoisan  

Yellow  silt  loam  

2170 

2000 

67380 

435 

Middle  Illinoisan  

Yellow  silt  loam  

1980 

1510 

65370 

535 

Upper  Illinoisan  

Yellow  silt  loam  

1900 

1610 

72570 

635 

Pre-Iowan  

Yellow  silt  loam  

2290 

1750 

76150 

735 

lowan  

Yellow  silt  loam  

2120 

1960 

71180 

1135 

Early  Wisconsin  

Yellow  silt  loam  

1870 

1590 

68690 

864 

Deep  loess.  . 

Yellow  fine  sandy  loam. 

2610 

1600 

71760 

Timber  uplands,  undulating. 


1034 

Yellow-gray  silt  loam  .  .  . 

2710 

1390 

111100 

760 

lowan  

3920 

1590 

54300 

Sand,  swamp,  and  bottom  lands. 


1331 

Old  bottom  lands  

Deep  gray  silt  loam  

2250 

1830 

68090 

1451 

Late  bottom  lands  

Brown  loam  

6660 

2160 

77540 

1481 

Sand  plains  and  dunes  .  • 

Sand  soil  

2070 

1480 

62690 

1401 

Late  swamp.         

Deep  peat  

64980 

2940 

7010 

COMPARISON  OF  DIFFERENT  TYPES  AND  DEPTHS  OF  SOIL 

Before  passing  on  to  the  discussion  of  the  composition  and  needs 
of  the  individual  soil  types  and  of  results  already  secured  from  dif- 
ferent methods  of  soil  treatment  or  improvement,  let  us  study 
briefly  the  general  information  given  in  Tables  3,  4,  and  5. 


THE  FERTILITY  IN  ILLINOIS  SOILS. 


201 


TABLE  5. — FERTILITY  IN  ILLINOIS  SOILS 
Average  Pounds  per  Acre  in  Subsoil  (20-40  inches) 


Soil 
type 
No. 

Soil  area  or 
glaciation. 

Soil  type. 

Total 
nitro- 
gen. 

Total 
phos- 
phorus. 

Total 
potas- 
sium. 

Prairie  lands,  undulating-. 


330 

Lower  Illinoisan  

Gray  silt  loam  on  tight 

clay  

3240 

2400 

84300 

426 

Middle  Illinoisan. 

Brown  silt  loam  

3440 

2680 

90040 

526 

Upper  Illinoisan 

Brown  silt  loam   

3440 

2790 

98580 

626 

Pre-Iowan  

Brown  silt  loam  

3940 

3380 

102620 

726 

lowan  

Brown  silt  loam  

3540 

2780 

99780 

1126 

Early  Wisconsin  

Brown  silt  loam  

3420 

2620 

117880 

1026 

Late  Wisconsin  

Brown  silt  loam  

3630 

2630 

160140 

Prairie  lands,  flat. 


420 

520 

1120 

1220 


Middle  Illinoisan. 
Upper  Illinoisan. . 
Early  Wisconsin . 
Late  Wisconsin  . . 


3020 
3140 
3490 
3180 


3030 
3640 
3630 
3930 


94900 

96220 

111280 

125370 


Timber  uplands,  rolling  or  hilly. 


135 

Unglaciated  

Yellow  silt  loam  

1970 

3280 

105430 

335 

Lower  Illinoisan  

Yellow  silt  loam  

2480 

3170 

99670 

435 

Middle  Illinoisan  

Yellow  silt  loam  

2820 

2810 

99000 

535 

Upper  Illinoisan  

Yellow  silt  loam  

2280 

3270 

100950 

635 

Pre-Iowan  

Yellow  silt  loam. 

2380 

3400 

102100 

735 

lowan  

Yellow  silt  loam. 

2490 

3900 

105030 

1135 

Early  Wisconsin  

Yellow  silt  loami  

.  2450 

2660 

103830 

864 

Deep  loess.  .  , 

Yellow  fine  sandy  loam.  . 

2730 

3320 

105210 

Timber  uplands,  undulating. 


1034 

Late  Wisconsin  

Yellow-gray  silt  loam 

3240 

2400 

156740 

760 

Brown  sandy  loam  

4160 

2440 

81180 

Sand,  swamp,  and  bottom  lands. 


1331 

Old  bottom  lands  

Deep  gray  silt  loam  

2280 

2620 

101610 

1451 

Late  bottom  lands  

Brown  loam  

4150 

2410 

119520 

1481 

Sand  plains  and  dunes.  . 

Sand  soil  :  

3100 

2230 

94030 

1401 

Late  swamp.  . 

Deep  peat.  . 

97730 

3740 

11510 

The  undulating  prairie  lands  are  arranged  in  order  of  age,  the 
Lower  Illinoisan  being  the  oldest  glaciation  and  the  Late  Wiscon- 
sin being  the  most  recent.  As  we  pass  from  the  oldest  to  the  new- 
est soils  there  is  a  somewhat  regular  increase  in  plant  food  content. 
These  nearly  level  or  gently  undulating  prairie  soils  are  less  affected 
mechanically  with  the  passing  years  than  are  other  soils,  such  as 
the  rolling  hill  lands,  which  lose  by  surface  washing,  or  the  bottom 
lands,  which  frequently  receive  deposits  from  overflow. 


202  BULLETIN  No.  123.  [February, 

There  are  some  marked  evidences  in  morainal  deposits  and  in 
soil  composition  of  considerable  differences  in  time  of  formation  be- 
tween the  Lower  Illinoisan,  the  Middle  Illinoisan,  the  Early  Wis- 
consin, and  the  Late  Wisconsin  glaciation  and  corresponding  loes- 
sial  deposits,  but  less  marked  evidences  of  any  long  periods  of  time 
having  elapsed  between  the  Middle  Illinoisan,  Upper  Illinoisan, 
Pre-Iowan,  and  lowan.  Because  of  this  the  best  comparison  is 
made  with  the  four  areas  first  mentioned.  The  phosphorus  varies 
in  these  soils  from  840  to  1170,  1190,  and  1410,  and  the  potassium 
from  about  25,000  to  32,000,  36,000,  and  45,000  pounds  per  acre 
in  the  surface  soil. 

With  the  black  clay  loams  which  occupy  some  of  the  flat  prairie 
lands,  there  are  also  some  such  relations  indicated,  although  this 
type  of  soil  is  likely  to  be  modified  somewhat  because  of  more  or 
less  deposit  from  overflows. 

In  the  case  of  the  yellow  silt  loams  of  the  hill  lands,  which  are 
always  subject  to  more  or  less  surface  washing,  there  is  no  such 
gradation  with  the  age  of  formation,  because  all  of  these  soils  were 
in  the  recent  past  unweathered  subsoils  from  which  the  surface  soil 
has  been  washed  away  during  recent  centuries. 

Undoubtedly  the  lower  amounts  of  phosphorus  and  potassium 
in  the  prairie  land  of  the  Lower  Illinoisan  glaciation  as  compared 
with  the  Late  Wisconsin  glaciation  is  in  large  part  due  to  loss  by 
longer  weathering  and  leaching  of  the  older  formation  during  the 
long  period  of  time  that  intervened  between  the  earlier  and  later 
glaciers.  Potassium,  being  much  more  subject  to  loss  from  weath- 
ering and  leaching,  is  a  better  measure  of  this  action  than  phospho- 
rus. Even  in  the  <mbsoils  we  find  the  potassium  varying  from  84,- 
ooo  pounds  in  the  Lower  Illinoisan  to  118,000  in  the  Early  Wis- 
consin and  160,000  in  the  Late  Wisconsin  glaciation. 

The  nitrogen  is  a  very  good  measure  of  the  humus,  or  organic 
matter,  being  contained  almost  entirely  in  the  organic  matter,  and 
consequently  soils  that  are  rich  in  phosphorus  and  potassium  and 
highly  productive  for  legumes  and  other  plants  are  likely  to  be  cor- 
respondingly richer  in  nitrogen  than  are  soils  poorer  in  the  mineral 
elements. 

While  some  of  the  phosphorus  is  always  contained  in  the  organic 
matter  present  in  the  soil,  phosphorus  being  one  of  the  constituents 
of  humus,  by  far  the  larger  part  of  the  phosphorus  is  in  mineral 
form ;  while  the  potassium  is  almost  exclusively  in  the  mineral  form. 

If  a  constituent  were  present  uniformly  in  the  different  soil 
depths,  then  Table  4  would  show  twice  as  much,  and  Table  5  three 
times  as  much  of  such  a  constituent  as  Table  3,  because  the  amounts 
of  soil  represented  in  the  surface,  subsurface,  and  subsoil  are  two 


iyo8.]  THE  FERTILITY  IN  ILLINOIS  SOILS.  203 

million,  four  million,  and  six  million  pounds,  respectively.  With 
potassium,  in  the  yellow  silt  loam  hill  soils,  this  ratio  obtains  with 
some  degree  of  uniformity.  Thus,  for  the  Lower  Illinoisan  glacia- 
tion  the  average  amounts  are  32,000,  67,000,  and  100,000,  in  pounds 
for  the  respective  strata,  and  for  the  Middle  Illinoisan  glaciation  they 
are  33,000,  65,000,  and  99,000;  while  33,000,  66,000,  and  99,000 
would  express  the  exact  ratio.  The  ratio  is  exact  with  the  lowan 
brown  sandy  loam,  the  amounts  of  potassium  being  in  round  num- 
bers 27,000,  54,000,  and  81,000  pounds  per  acre  for  the  three  strata, 
surface,  subsurface,  and  subsoil. 

Some  noticeable  variations  from  this  rule  are  the  undulating 
prairie  lands  of  the  Lower  Illinoisan  and  Late  Wisconsin  glacia- 
tions,  the  potassium  numbers  being  for  the  Lower  Illinoisan  glacia- 
tion 25,000,  54,000,  and  84,000  instead  of  25,000,  50,000,  and 
75,000;  and  for  the  Late  Wisconsin  45,000,  96,000,  and  160,000 
instead  of  45,000,  90,000,  and  135,000. 

These  variations  may  be  explained  perhaps  by  the  longer  weath- 
ering and  more  thorough  leaching*  of  the  surface  soil  of  the  older 
southern  Illinois  area,  influenced  also  by  the  tight  clay  subsoil,  and 
by  the  fact  that  in  the  Late  Wisconsin  area  the  loessial  deposit  is 
quite  shallow,  and  the  subsoil,  even  above  40  inches,  may  have  been 
somewhat  modified  by  glacial  material. 

The  nitrogen,  as  already  explained,  is  contained  almost  entirely 
in  the  humus,  or  organic  matter,  of  the  soil.  Indeed  the  humus  is  a 
fairly  good  index  of  the  nitrogen  content  of  the  soil.  As  would  be 
expected  from  this  the  nitrogen  content  of  most  subsoils  is  very  low 
because  they  contain  but  little  humus.  Thus  in  the  Late  Wisconsin 
black  clay  loam  there  are  8900  pounds  of  nitrogen  in  the  surface 
seven  inches,  while  in  the  20  inches  of  subsoil,  instead  of  finding 

*A  theory  has  been  recently  emphasized  by  Doctor  F.  K.  Cameron  of  the 
United  States  Bureau  of  Soils  (Cyclopedia  of  American  Agriculture  (1907)  I., 
370),  to  the  effect  that  plant  food  tends  to  accumulate  in  the  surface  soil,  the 
assumption  being  that  larger  amounts  of  soluble  matter  are  brought  up  by  the 
rise  of  capillary  water  than  are  carried  down  by  the  descent  of  rain  water. 
While  this  is  well  known  to  be  the  case  in  arid  or  semi-arid  regions  where  water 
leaves  the  soil  not  by  drainage  but  only  by  evaporation,  it  is  fully  disproved 
for  normal  agricultural  regions,  not  only  by  the  fact  that  drainage  waters  always 
carry  off  some  soluble  plant  food,  but  also  by  the  fact,  as  illustrated  in  the 
above  example,  that  old  surface  soils  are  poorer  than  the  corresponding  sub- 
soils and  lower  subsoils  in  potassium,  magnesium,  lime  and  other  materials 
that  dissolve  in  the  soil  waters.  The  constituents  that  tend  to  accumulate  in 
the  surface  soils  in  humid  regions  are  deposited  there  as  a  part  of  the  plant 
residues  and  include  humus,  organic  nitrogen,  and  organic  phosphorus,  previously 
brought  to  the  surface  through  the  plant  roots. 

One  of  the  best  methods,  and  certainly  the  most  common  method,  used  by 
geologists  for  ascertaining  the  relative  age  of  different  soils  is  to  determine  the 
depth  of  soil  from  which  some  mineral  constituent,  as  lime,  has  been  leached  out ; 
whereas,  according  to  the  above  theory,  "there  is  a  steady  tendency  toward  an 
accumulation  of  dissolved  mineral  matter  at  the  surface." 


204  BULLETIN  No.  123.  [February, 

three  times  as  much  (as  would  be  expected  with  potassium)  we  find 
only  one-third  as  much  total  nitrogen  (3180  pounds).  In  other 
words,  the  surface  soil  is  nearly  nine  times  as  rich  in  nitrogen  as 
the  subsoil,  equal  weights  of  soil  being  considered. 

With  badly  worn  or  washed  soils,  as  the  yellow  silt  loams  of  the 
hill  lands,  the  surface  may  contain  but  little  more  nitrogen  than  an 
equal  weight  of  subsoil,  making  the  maintenance  of  humus  and 
nitrogen  by  far  the  most  important  problem  for  such  soils. 

A  study  of  the  phosphorus  content  of  the  surface,  sub-surface, 
and  subsoil  of  the  different  groups  of  type  soils  plainly  indicates, 
as  already  explained,  that  phosphorus  is  in  part  associated  with  ni- 
trogen in  the  humus  and  in  larger  part  contained  in  the  mineral  mat- 
ter with  the  potassium.  The  surface  of  the  brown  silt  loam  undu- 
lating prairie  lands  averages  about  one-half  richer  in  phosphorus 
than  the  surface  of  the  hill  lands  but  there  is  no  such  difference  in 
the  phosphorus  content  of  the  subsoils  of  those  groups.  Even  be- 
tween 20  and  40  inches  these  subsoils  are  much  alike,  and  doubt- 
less they  are  more  nearly  alike  at  or  below  the  4O-inch  depth,  be- 
cause even  below  20  inches  there  is  appreciably  more  humus  and 
nitrogen  in  the  prairie  soils  than  in  the  hill  lands. 

Within  the  group  of  undulating  prairie  soils  the  phosphorus  con- 
tent of  the  surface  seven  inches  varies  from  840  to  1400  pounds  per 
acre  with  a  somewhat  greater  variation  in  nitrogen  and,  of  course, 
in  humus  also,  but  in  the  subsoils  this  variation  almost  disappears 
not  only  for  nitrogen  but  also  for  phosphorus. 

Thus,  we  have  in  the  soil  chiefly  organic  nitrogen  (in  humus) 
and  chiefly  inorganic  potassium  (in  mineral  form),  but  we  have 
both  organic  phosphorus  and  inorganic  phosphorus.  If  we  assume 
that  the  mineral  part  of  the  soil  is  of  approximately  uniform  compo- 
sition in  surface,  subsurface,  and  subsoil,  where  such  is  indicated 
by  the  potassium  content,  then  we  have  a  method  for  computing  the 
amount  of  phosphorus  that  is  organic  and  the  amount  that  is  in  the 
inorganic  or  mineral  form,  in  the  surface  soil. 

Thus,  in  the  Upper  Illinoisan  brown  silt  loam  the  potassium 
amounts  to  33,000  pounds  in  two  million  of  surface  soil  and  to  99,- 
ooo  pounds  in  six  million  of  subsoil,  suggesting  a  uniform  mineral  - 
composition.  The  two  million  pounds  of  surface  soil  contain  4840 
pounds  of  nitrogen  and  1200  pounds  of  phosphorus,  while'  two  mil- 
lion pounds  of  the  subsoil  would  contain  1150  pounds  of  nitrogen 
and  930  pounds  of  phosphorus.  By  subtracting  we  find  that  270 
pounds  of  phosphorus  appear  to  be  associated  with  3690  pounds 
of  nitrogen,  or  by  the  same  ratio  it  appears  that  about  390  pounds 
of  phosphorus  are  associated  with  the  4840  pounds  of  nitrogen  con- 
tained in  the  humus  in  the  surface  soil.  On  this  basis  nearly  one- 


/po<?.]  THE  FERTILITY  IN  ILLINOIS  SOILS.  205 

third  of  the  phosphorus  in  this  surface  soil  is  organic*  and  two- 
thirds  inorganic,  or  mineral,  although  for  other  types  of  soil  very 
different  proportions  of  organic  and  inorganic  phosphorus  may 
be  found. 

These  considerations  suggest  an  additional  reason  for  emphasiz- 
ing that  "humus  is  the  life  of  the  soil,"  for  in  its  decomposition 
products  both  nitrogen  and  phosphorus  are  liberated  in  forms  avail- 
able for  plant  growth".  It  is  also  suggested  that  while  old  and  rela- 
tively inactive  humus  if  present  in  sufficient  amount  may  aid  in  the 
production  of  large  crops  by  supplying  the  necessary  nitrogen  and 
phosphorus  from  its  own  constitution  as  it  slowly  decomposes  in 
the  soil,  its  decay  might  have  but  little  effect  in  liberating  phospho- 
rus from  the  mineral  compounds  contained  in,  or  applied  to,  the 
soil.  To  accomplish  this  result  satisfactorily  requires  the  action 
brought  about  by  the  bacteria  and  the  various  decomposition  pro- 
ducts of  the  more  active,  fresh,  fermenting  organic  matter,  as  farm 
manure,  legume  crop  residues,  or  other  green  manures. 

AVAILABLE  PLANT  FOOD 

"Available  plant  food"  is  an  expression  much  used  in  connection 
with  commercial  fertilizers,  and  the  argument  is  commonly  made 
that  because  the  soil  does  not  contain  available  plant  food,  we 
should  therefore  apply  available  plant  food  in  commercial  fertilizers. 
Instead  of  following  this  advice,  however,  the  farmer  should  adopt 
a  system  of  farming  that  will  make  available  the  plant  food  in  the 
soil  so  far  as  practicable,  and,  if  any  element  is  actually  deficient  in 
the  soil,  apply  that  element  in  cheap  form  and  in  positively  larger 
quantities  than  will  be  removed  in  large  crops;  and  then  make  it, 
too,  available  by  his  method  of  farming. 

There  are  three  methods  of  determining  with  some  degree  of 
satisfaction  which  elements,  if  any,  are  deficient  in  the  soil : 

First,  we  may  compute  from  Tables  i  and  3  the  probable  dura- 
bility of  a  soil  with  reference  to  any  element  of  plant  food.  Thus, 
we  can  determine  that  the  unglaciated  yellow  silt  loam  surface  soil 
contains  sufficient  nitrogen  for  less  than  20  large  corn  crops  if  only 
the  grain  were  removed ;  while  the  potassium  in  the  Late  Wiscon- 
sin brown  silt  loam  is  sufficient  for  more  than  2300  such  crops. 

Second,  we  can  assume  for  a  rough  estimation  that  the  equiva- 
lent of  2  percent  of  the  nitrogen,  I  percent  of  the  phosphorus,  and 

*It  may  be  that  some  portion  of  this  phosphorus  which  apparently  is  or 
has  been  associated  with  the  nitrogen  in  the  organic  form  ultimately  passes  into 
difficultly  soluble  inorganic  phosphorus  compounds  by  uniting  with  the  iron  or 
aluminum  in  the  surface  soil. 


206  BULLETIN  No.  123.  [February, 

54  of  i  percent  of  the  total  potassium  contained  in  the  surface  soil 
(Table  3)  can  be  made  available  during  one  season  by  practical 
methods  of  farming.  Of  course,  the  percentage  that  can  be  made 
available  will  vary  much  with  different  seasons,  with  different  soils, 
and  for  different  crops ;  and  yet  with  normal  soils  and  seasons  and 
for  ordinary  crops  the  above  percentages  represent  roughly  about 
the  proportion  that  is  liberated  from  the  soil  j>f  the  element  that 
limits  the  yield  of  the  crop. 

In  Table  6  are  given  the  amounts  of  annually  available  plant 
food  as  roughly  estimated  by  this  method  of  computation. 

Of  course,  these  amounts  would  become  smaller  and  smaller 
year  by  year  in  proportion  as  the  total  supply  is  decreased,  and 
accordingly  complete  exhaustion  is  not  only  impracticable  and  un- 
profitable because  of  the  continual  reduction  in  crop  yields,  but  it  is 
mathematically  impossible,  just  as  it  would  be  impossible  to  ex- 
haust a  bank  account  if  only  i  percent  of  the  remaining  deposit 
could  be  withdrawn  each  week. 

A  peaty  swamp  soil  containing  2930  pounds  of  total  potassium 
per  acre  in  the  first  seven  inches  would  liberate  during  the  season 
according  to  this  estimate  about  7  pounds  of  potassium,  which 
would  be  equivalent  to  a  crop  of  10  bushels  of  corn,  which  repre- 
sents roughly  about  the  average  yield  from  such  land  when  not 
treated  with  potassium,  as  is  shown  in  the  following  pages.  The 
common  brown  silt  loam  prairie  soil  when  well  farmed  will  aver- 
age about  50  bushels  of  corn  per  acre,  which  would  require  11^2 
pounds  of  phosphorus  and  74  pounds  of  nitrogen,  while  12  and  96 
pounds  represent  i  percent  of  the  phosphorus  and  2  percent  of  the 
nitrogen,  respectively,  in  the  surface  soil,  where  phosphorus  is  the 
first  limiting  element. 

These  illustrations  are  given  not  to  prove  that  this  rough  esti- 
mation is  applicable,  but  rather  to  show  the  basis  which  suggests 
such  a  computation.  It  has  some  value,  chiefly,  perhaps,  in  that  it 
helps  one  to  understand  why  it  is  that  with  phosphorus  enough  in 
the  surface  soil  for  50  crops,  we  obtain  only  half  a  crop  as  an 
average. 

On  this  basis  we  should  try  to  keep  sufficient  phosphorus  in  the 
surface  soil  for  100  large  crops,  of  which  i  percent  would  then  be 
sufficient  for  one  large  crop.  This  would  require  about  2300 
pounds  of  phosphorus  per  acre,  or  but  little  more  than  is  actually 
contained  in  our  most  productive  corn  belt  soil,  as  the  Early  Wis- 
consin black  clay  loam  in  such  counties  as  McLean,  Champaign, 
Edgar,  et  al.  (see  Table  3  and  the  appendix). 


1908.] 


THE  FERTILITY  IN  ILUNOIS  SOILS. 


207 


TABLE  6.— ANNUALLY  AVAILABLE  FERTILITY  IN  ILLINOIS  SOILS, 
ROUGHLY  ESTIMATED;  POUNDS  PER  ACRE    • 


Soil 
type 
No. 

Soil  area 
or 
glaciation. 

Soil  type. 

Avail- 
able 
nitro- 
g-en. 

Avail- 
able 
phos- 
phorus. 

Avail- 
able 
potas- 
sium 

Prairie  lands,  undulating. 


330 

Lower  Illinoisan  

Gray  silt  loam  on  tight 

clay  .  . 

58 

8 

62 

426 

Middle  Illinoisan  

Brown  sill  loam  

87 

12 

81 

526 

Upper  Illinoisan  

Brown  silt  loam  

97 

12 

82 

626 

Pre-Iowan  

86 

12 

88 

726 

lowan  

Brown  silt  loam  

98 

12 

82 

1126 

Brown  silt  loam  

101 

12 

91 

1026 

Late  Wisconsin  

Brown  silt  loam  

135 

14 

113 

Prairie  lands,  flat. 


420 

Middle  Illinoisan  

Black  clay  loam  

108 

14 

80 

520 

Upper  Illinoisan  

Black  clay  loam  

135 

17 

74 

1120 

Karly  Wisconsin. 

Black  clay  loam  

157 

20 

88 

1220 

Late  Wisconsin.  . 

Black  clay  loam.  .  , 

178 

19 

93 

Timber  uplands,  rolling  or  hilly. 


135 

Unglaciated  

Yellow  silt  loam  

38 

10 

79 

335 

Lower  Illinoisan  

Yellow  silt  loam  

43 

10 

80 

435 

Middle  Illinoisan  .  .    .  . 

Yellow  silt  loam  

37 

8 

82 

535 

Upper  Illinoisan  

Yellow  silt  loam  

40 

8 

87 

635 

Pre-Iowan  

Yellow  silt  loam  

48 

9 

93 

735 

lowan  

Yellow  silt  loam  

38 

9 

89 

1135 

38 

9 

82 

864 

Deep  loess  

Yellow  fine  sandy  loam  .  .  . 

43 

10 

89 

Timber  uplands,  undulating. 


1034 

Late  Wisconsin  

Yellow-gray  silt  loam 

58 

8 

119 

760 

lowan  

Brown  sandy  loam  

61 

9 

67 

Sand,  swamp,  and  bottom  lands. 


1331 

Old  bottom  lands  .... 

Deep  gray  silt  loam  

72 

14 

91 

1451 

Late  bottom  lands  

94 

16 

100 

1481 

Sand  plains  and  dunes. 

29 

8 

77 

1401 

Late  swamp.  .  . 

Deep  peat  .  . 

m* 

20 

7 

*The  nitrogen  in  peat  is  so  very  slowly  available  that  not  even  a  rough 
estimate  can  be  made  here. 

Third,  we  may  apply  different  elements  of  plant  food  to  the 
soil  and  note  the  effect,  if  any,  in  increasing  the  yield  of  crops,  and 
thus  sometimes  discover  what  element  is  most  deficient  in  the  soil. 
One  might  suppose  that  this  would  be  the  best  method,  but  such  is 


208  BULLETIN  No.  123.  [February, 

not  the  case.  This  method  frequently  gives  erroneous  results  which 
if  followed  may  lead  to  land  ruin,  because  the  substance  applied 
may  produce  little  or  no  benefit  on  account  of  the  special  plant  food 
element  it  contains  but  it  may  act  as  a  powerful  soil  stimulant  and 
thus  liberate  from  the  soil  some  other  entirely  different  element  in 
which  the  soil  is  already  becoming  deficient.  Thus  have  many  lands 
been  practically  ruined  by  the  use  of  landplaster  and  salt,  by  the 
improper  use  of  lime,  and  even  by  the  use  of  clover  merely  as  a  soil 
stimulant.  Some  good  illustrations  of  this  action  of  soluble  salts 
are  shown  in  the  following  pages. 

"In  considering  the  general  subject  of  culture  experiments  for 
determining  fertilizer  needs,  emphasis  must  be  laid  on  the  fact  that 
such  experiments  should  never  be  accepted  as  the  sole  guide  in  de- 
termining future  agricultural  practice.  If  the  culture  experiments 
and  the  ultimate  chemical  analysis  of  the  soil  agree  in  the  deficiency 
of  any  plant  food  element,  then  the  information  is  conclusive  and 
final;  but  if  these  two  sources  of  information  disagree,  then  the 
culture  experiments  should  be  considered  as  tentative  and  likely  to 
give  way  with  increasing  knowledge  and  improved  methods  to  the 
information  based  on  chemical  analysis,  which  is  absolute."* 

PHOSPHORUS 

In  studying  the  field  experiments  reported  below  it  is  most  im- 
portant to  keep  in  mind  the  amounts  of  phosphorus  applied  to  and 
removed  from  the  soil  as  well  as  the  cost  of  the  phosphorus  applied. 
For  reasons  already  explained,  and  completely  established  by  the 
data  and  results  secured,  phosphorus  is  the  only  element  that  must 
be  purchased  and  returned  to  our  most  common  soils.  Phosphorus 
is  the  key  to  permanent  agriculture  on  these  lands.  To  maintain  or 
increase  the  amount  of  phosphorus  in  the  soil  makes  possible  the 
growth  of  clover  and  the  consequent  addition  of  nitrogen  from  the 
inexhaustible  supply  in  the  air;  and,  with  the  addition  of  .decaying 
organic  matter  in  clover  residues  and  in  manure  made  in  large  part 
from  clover  hay  and  pasture  and  from  the  larger  crops  of  corn 
which  clover  helps  to  produce,  comes  the  possibility  of  liberating 
from  the  immense  supply  in  the  soil  sufficient  potassium,  when  sup- 
plemented by  that  returned  in  manure  and  crop  residues,  for  the 
production  of  large  crops  at  least  for  thousands  of  years ;  whereas 
if  the  supply  of  phosphorus  in  the  soil  is  steadily  decreased  in  the 
future  in  accordance  with  the  present  most  common  farm  practice, 
then  poverty  is  the  only  future  for  the  people  who  till  the  common 
prairie  lands  of  Illinois.  And  this  does  not  refer  to  the  far  distant 

*Cyclopedia  of  American  Agriculture,  Volume  i,  page  475. 


/potf.J  THE  FERTILITY  IN  ILLINOIS  SOILS.  209 

future  only,  for  the  turning  point  is  already  past  on  many  Illinois 
farms,  and  lands  that  have  passed  their  prime  with  60  years  of  cul- 
tivation will  decrease  rapidly  in  productive  power  and  in  value 
during  another  sixty  years  of  similar  exhaustive  farm  practice. 

On  land  deficient  in  phosphorus  the  standard  rule  should  be  to 
apply  phosphorus  equivalent  to  25  pounds  of  the  element  per  acre 
per  annum,  remembering  that  a  loo-bushel  crop  of  corn  removes  23 
pounds  of  phosphorus.  To  supply  25  pounds  of  phosphorus  will 
require  200  pounds  of  good  steamed  bone  meal,  costing  about  $2.50, 
or  200  pounds  of  good  raw  rock  phosphate,  costing  about  80  cents, 
or  \2.l/2.  tons  of  average  fresh  farm  manure,  or  the  manure  that 
can  be  made  from  200  bushels  of  corn,  costing  $70  or  $80  as  feed. 

Probably  the  most  practical  and  profitable  method  of  maintain- 
ing the  supply  of  phosphorus  is  by  applying  1000  pounds  per  acre 
of  raw  rock  phosphate  once  every  five  or  six  years,  preferably  in 
connection  with  all  available  farm  manure,  and  for  the  first  two 
or  three  applications  one  ton  per  acre  of  the  phosphate  may  well  be 
used.  It  will  remain  in  the  soil  until  removed  by  crops  unless  sub- 
ject to  surface  washing. 

If  one  adopts  the  rule  that  when  he  applies  phosphorus  it  must 
be  at  the  rate  of  at  least  25 'pounds  per  acre  for  each  crop  in  the 
rotation  (not  25  pounds  of  so-called  phosphoric  acid,  nor  25  pounds 
of  so-called  bone  phosphate,  but  25  pounds  of  phosphorus),  he  will 
then  be  proof  against  the  misleading  and  ruinous  practice  of  using 
ordinary  so-called  complete  commercial  fertilizers,  for  he  will  at 
once  discover  that  to  buy  25  pounds  of  phosphorus  in  such  fertilizers 
will  cost  from  $8.00  to  $10.00,  and  that  the  amounts  he  can  afford 
to  apply  of  such  fertilizers  will  not  furnish  more  than  J4  to  ^  as 
much  phosphorus  as  is  actually  removed  from  the  soil  in  good  crops. 

In  the  field  experiments  reported  in  this  bulletin  the  standard 
application  of  phosphorus  in  steamed  bone  meal  is  at  the  rate  of 
25  pounds  per  acre  for  each  year  in  the  rotation.  This  requires  600 
pounds  of  bone  for  a  three-year  rotation,  800  pounds  for  a  four- 
year  rotation,  etc.  When  raw  rock  phosphate  is  used,  about  three 
times  as  much  is  applied,  which  adds  three  times  as  much  phospho- 
rus to  the  soil  but  at  about  the  same  cost  as  for  the  bone.  After 
two  or  three  rotations  the  amount  of  rock  phosphate  to  be  applied 
will  be  reduced  to  one-third  of  the  present  applications. 

Where  farm  manure  is  used  the  amount  applied  to  any  plot  is 
in  direct  proportion  to  the  total  crop  yields  of  the  previous  rotation. 
Thus,  if  the  use  of  phosphorus  increases  the  yield  of  crops  in  a  ro- 
tation, it  will  likewise  increase  the  possible  production  of  manure, 
and  consequently  the  application  of  manure  is  increased  for  the  next 
rotation  on  plots  where  phosphorus  and  manure  are  used.  Our 


210  '        BULLETIN  No.  123.  [February, 

present  plan  is  to  apply  the  same  number  of  tons  per  acre  of  aver- 
age fresh  manure  (25  percent  dry  matter)  as  the  number  of  tons 
of  air-dry  produce  harvested,  which  requires  about  two-thirds  of 
the  produce  to  be  used  for  feed  and  bedding  and  allows  for  a  loss  in 
practice  of  20  percent  of  the  manure  produced. 

INDIVIDUAL  TYPES  OF  ILLINOIS  SOIL 

In  the  tabular  statements  (Tables  3,  4,  and  5)  an  absolute  in- 
voice is  given  concerning  the  stocks  of  plant  food  contained  in 
twenty-five  of  the  principal  types  of  soil  in  Illinois.  In  the  follow- 
ing description  of  the  results  obtained  from  pot  cultures  and  field 
experiments  and  of  systems  of  soil  improvement  adapted  to  these 
different  types,  it  is  necessary  in  some  cases  to  discuss  a  single  type 
in  a  single  area,  but  so  far  as  practicable  similar  types  will  be  dis- 
cussed in  groups.  It  is  the  purpose  of  this  bulletin  to  make  the 
descriptions  of  each  soil  type  sufficiently  complete  so  that  the  read- 
ing farmer  or  landowner  will  recognize  the  soil  of  his  own  farm. 

Of  course,  there  are  minor  soil  types  and  abnormal  soils  which 
will  require  the  completion  of  the  detail  soil  survey  by  counties  (a 
work  which  is  already  well  advanced),  but  three- fourths  of  the 
farmers  of  the  state  should  be  able  to  obtain  from  this  bulletin  some 
definite  information  applying  directly  to  the  stock  of  fertility  con- 
tained in  the  soil  of  their  own  farms  and  even  a  larger  number  can 
profit  by  the  adoption  of  suggested  systems  of  soil  improvement. 

GRAY  SILT  LOAM  ON  TIGHT  CLAY  (330) 

This  type  of  soil  is  the  commonest  prairie  land  in  the  Lower 
Illinoisan  glaciation.  This  soil  area  is  marked  with  the  number 
3  on  the  colored  general  survey  soil  map  of  Illinois.  It  lies  chiefly 
between  the  Kaskaskia  and  Wabash  rivers  and  is  bounded  on  the 
south  by  the  Ozark  Hills  and  on  the  north  by  the  terminal  moraine 
of  the  Wisconsin  glaciation  which  passes  through  Shelby,  southern 
Coles,  and  Edgar  counties.  This  area  includes  all  of  the  counties 
of  Fayette,  Effmgham,  Jasper,  Marion,  Clay,  Richland,  Washing- 
ton, Jefferson,  Wayne,  Perry,  Franklin,  and  Hamilton,  and  parts  of 
Montgomery,  Shelby,  Cumberland,  Clark,  Crawford,  Lawrence, 
Wabash,  Edwards,  White,  Saline,  Williamson,  Jackson,  Randolph, 
Monroe,  St.  Clair,  Clinton,  and  Bond. 

In  most  of  these  counties  the  gray  silt  loam  prairie  soil  (330) 
is  the  most  common  type,  although  it  is  not  the  only  type  in  any 
county  and  probably  not  the  only  type  in  any  township. 

This  type  of  soil  is  well  known  and  everywhere  recognized  by 
the  farmers  themselves  as  "the  common  hardpan  prairie."  It  con- 


/po5.]  THE  FERTILITY  IN  ILLINOIS  SOILS.  211 

sists  of  a  friable  gray  silt  loam  which  commonly  varies  in  depth 
from  6  to  12  inches  and  below  which  is  a  light  gray  or  nearly  white 
layer,  or  stratum,  of  slightly  loamy  silt  varying  from  less  than  one 
inch  to  more  than  10  inches  in  thickness,  and  commonly  referred 
to  as  the  "gray  layer."  At  a  depth  of  16  to  20  inches  the  soil  is 
underlain  by  a  tight  clay  subsoil,  frequently  termed  "hardpan." 

It  should  be  understood,  however,  that  this  subsoil  is  not  true 
hardpan,  which  consists  of  sand  or  gravel  cemented  together  with 
clay  to  form  a  substance  which  is  practically  impervious  to  water 
and  through  which  ditches  cannot  be  dug  with  only  a  spade.  No 
true  hardpan  subsoil  has  yet  been  found  anywhere  in  Illinois,  unless 
it  has  been  at  considerable  depths,  as  in  the  digging  of  wells. 

The  subsoil  of  this  gray  silt  loam  prairie  is  a  tight  clay,  inclined 
to  be  gummy.  Water  passes  through  it,  although  quite  slowly,  and 
when  wet  it  can  be  spaded  without  special  difficulty,  but  when  dry 
it  becomes  stiff  and  hard. 

Where  this  soil  is  enriched  by  proper  treatment  excellent  crops 
are  grown  in  seasons  of  normal  rainfall,  but  they  are  likely  to  suffer 
in  times  of  drouth  more  than  would  be  the  case  with  a  better  subsoil. 
As  a  rule  the  rainfall  in  southern  Illinois  is  abundant  and  well  dis- 
tributed during  the  growing  season  and  where  the  top  soil  is  kept 
fertile  severe  injury  from  drouth  is  not  common. 

From  Table  3  it  will  be  seen  that  the  average  surface  soil  of 
this  type  contains  per  acre  2880  pounds  of  nitrogen,  840  pounds  of 
phosphorus,  and  24,940  pounds  of  potassium,  and  that  it  requires 
an  application  of  2  to  5  tons  of  ground  limestone.  Compared  with 
the  requirements  for  a  practical  crop  rotation  this  soil  is  very  poor 
in  phosphorus  and  very  deficient  in  lime.  Compared  with  the  com- 
position of  fertile  soils  it  is  also  deficient  in  humus  as  indicated  by 
the  total  nitrogen. 

It  will  be  seen  from  Tables  i  and  3  that  50  bushels  of  wheat 
(grain  only)  remove  from  the  land,  and  from  the  farm  if  sold,  12 
pounds  of  phosphorus  and  13  pounds  of  potassium;  and  that  the 
total  amounts  of  these  elements  in  the  surface  soil  of  this  type  are 
sufficient  to  supply  the  phosphorus  for  70  years  and  the  potassium 
for  1900  years,  provided  they  could  be  liberated  as  needed;  or,  if 
both  grain  and  straw  were  removed,  the  phosphorus  is  equal  to  52 
such  crops  and  the  potassium  to  520  crops. 

It  should  be  understood  that  the  plant  food  contained  in  all 
soils  is  almost  entirely  in  insoluble  form,  that  growing  crops  can 
take  up  plant  food  only  in  soluble  form,  and  that  one  of  the  prob- 
lems always  to  be  considered  is  how  to  enable  the  growing  crops  to 
secure  sufficient  plant  food  for  maximum  yields.  If  by  the  best 
systems  of  crop  rotations,  with  proper  use  of  green  manures,  and 


212  BULLETIN  No.  123.  [February, 

in  favorable  seasons,  we  can  liberate  the  equivalent  of  i  percent  of 
the  phosphorus  contained  in  the  surface  soil,  it  would  amount  to 
about  8  pounds  per  acre  for  the  first  year  for  the  type  of  soil  under 
consideration.  This  would  be  sufficient  for  a  25-bushel  crop  of 
wheat.  If  with  less  perfect  systems  only  half  of  i  percent  is  lib- 
erated, it  would  amount  to  4  pounds,  or  enough  for  a  12-bushel 
crop  of  wheat. 

On  the  University  soil  experiment  field  near  Odin,  Marion 
county,  on  this  ordinary  prairie  land  of  the  Lower  Illinoisan  glacia- 
tion,  wheat  is  grown  in  a  four-year  crop  rotation  with  clover,  corn, 
and  cowpeas.  By  having  four  different  series  of  plots  every  crop 
may  be  grown  every  year. 

As  an  average  of  the  last  four  years  (1904,  1905,  1906,  and 
1907),  wheat  grown  in  this  rotation  has  produced  nl/2  bushels 
per  acre  with  no  special  soil  treatment,  all  crops  having  been  re- 
moved. 

Where  one  cowpea  crop  and  some  catch  crops  (as  cowpeas 
seeded  in  the  corn)  had  been  plowed  under  during  the  rotation,  the 
average  yield  of  wheat  was  increased  to  14  bushels. 

Where  lime  or  ground  limestone  had  been  applied  and  the  cow- 
peas  also  plowed  under  the  average  yield  of  wheat  has  been  18^2 
bushels  per  acre.  On  this  set  of  plots  better  cowpea  crops  and  catch 
crops  have  been  produced  and  turned  under  as  green  manure,  be- 
cause the  soil  acidity  has  been  corrected  by  the  lime,  applied  for  the 
special  benefit  of  the  legume  crops. 

Where  phosphorus  has  been  applied  in  addition  to  the  use  of 
lime  and  green  manure,  the  average  yield  of  wheat  during  the  four 
years  has  been  27  bushels.;  and  where  potassium  also  has  been  in- 
cluded the  average  yield  has  been  29^2  bushels  of  wheat  per  acre. 

These  results  are  quite  in  harmony  with  what  might  be  expected 
from  the  chemical  composition  of  the  soil.  If,  however,  we  con- 
sider the  corn  crops  in  the  same  rotation  we  have  a  somewhat  dif- 
ferent set  of  results. 

•The  average  yield  of  corn  for  the  four  years  on  the  untreated 
rotated  land  has  been  38  bushels  per  acre;  with  legume  treatment 
(cowpeas  turned  under)  41  bushels;  with  legume  and  lime  treat- 
ment 45  bushels;  with  legume,  lime,  and  phosphorus  46  bushels; 
and  with  legume-lime-phosphorus-potassium  treatment  the  average 
yield  of  corn  for  four  years  has  been  61  bushels  per  acre.  (See 
Plates  i  and  2). 

For  more  convenient  comparison  these  results  are  shown  in 
Table  7. 


THE  FERTILITY  IN  ILLINOIS  SOILS.  213 

TABLE  7. — CROP  YIELDS  IN  SOIL  EXPERIMENTS:    ODIN  FIELD 


Gray  silt  loam  prairie 
Lower  Illinoisan  glaciation. 

Average  of  eight  tests  in  four  years; 
two  tests  each  year  for  each  crop, 
bushels  per  acre. 

Soil  treatment  applied. 

Wheat. 

Corn. 

11.6 

13.8 
18.5 
27.1 
29.5 

38.3 
40.8 
45.3 
46.2 
61.3 

Legume  (cowpeas  turned  under)  

Legume   lime   phosphorus  

Legume,  lime,   phosphorus,  potassium 

These  results  are  four-year  averages.  They  were  made  in  du- 
plicate each  year.  They  are  representative  and  trustworthy.  They 
have  also  been  confirmed  by  results  from  other  experiment  fields 
on  the  same  type  of  soil. 

The  effects  upon  corn  of  the  green  manure  alone  and  with  lime 
are  about  the  same  as  upon  wheat,  but  the  effects  produced  by  phos- 
phorus and  potassium  are  very  different  with  the  two  crops,  phos- 
phorus producing  the  largest  increase  in  wheat,  while  potassium  is 
much  more  effective  with  corn,  although  potassium  without  phos- 
phorus produces  less  increase  in  corn  than  when  applied  in  addition 
to  phosphorus. 

A  study  of  Table  i  will  show  that  a  6 1 -bushel  crop  of  corn  re- 
quires about  50  percent  more  potassium  than  a  3O-bushel  crop  of 
wheat,  which  fact  may  account  in  part  for  the  greater  effect  of  po- 
tassium on  corn,  although  about  the  same  relation  holds  for  phos- 
phorus. A  more  important  difference  probably  exists  in  the  relative 
feeding  powers  of  the  two  crops,  influenced  ( i )  by  the  difference  in 
root  systems,  including  the  different  depths  of  feeding,  (2)  by  the 
difference  in  seasonal  conditions  and  consequent  difference  in  de- 
cay of  humus  and  decomposition  of  other  soil  materials  and  in  ac- 
tivity of  soil  organisms  during  the  principal  periods  of  growth, 
(3)  by  the  solvent  action  of  the  carbon  dioxid  excreted  by  the  bac- 
teria and  from  the  plant  roots,  and  (4)  possibly  by  different  re- 
quirements as  to  the  forms  or  combinations  in  which  the  plant  food 
elements  can  be  absorbed  and  assimilated  or  utilized  by  corn  and 
wheat. 


214 


BULLETIN  No.  123. 


[February, 


PLATE  1. — CORN  CROP  (29.4  bu.)  WITH  NO  SOIL  TREATMENT.    ODIN  SOIL 
EXPERIMENT  FIELD,  1904. 


THE  FERTILITY  IN  ILLINOIS  SOILS. 


215 


PLATE  2 — CORN  CROP  (64.1  bu.)  WITH  L,EGUME-L/IME-PHOSPHORUS-POTAS- 
SITJM  TREATMENT.    ODIN  SOIL  EXPERIMENT  FIELD,  1904. 


216  BULLETIN  No.  123.  [February, 

A  further  very  important  question  is  whether  more  or  less  of 
the  effect  attributed  to  potassium  may  not  be  due  to  the  stimulating 
action  of  the  soluble  potassium  salt  in  liberating  other  substances 
from  the  soil  instead  of  serving  directly  as  plant  food;  and,  if  so, 
would  it  be  advisable  and  more  profitable  to  substitute  some  other 
less  expensive  material,  such  as  kainit,  for  the  concentrated  potas- 
sium sulfate  used  in  these  experiments. 

Information  is  accumulating  from  investigations  now  in  pro- 
gress which  will  help  to  solve  these  practical  problems. 

It  can  already  be  stated  that  as  an  average  of  28  tests  (includ- 
ing the  use  of  twenty-five  different  varieties  of  corn)  conducted  in- 
1907  on  the  University  experiment  field  near  Fairfield  in  Wayne 
county,  an  application  of  200  pounds  per  acre  of  potassium  sulfate, 
containing  85  pounds  of  the  element  potassium  and  costing  $5,  in- 
creased the  yield  of  corn  by  7  bushels  per  acre ;  while  600  pounds 
of  kainit  containing  only  60  pounds  of  potassium  and  costing  $4, 
gave  i  o.i  bushels  increase.  These  applications  are  made  but  once 
for  a  four-year  rotation.  The  kainit  with  25  pounds  less  potassium 
produced  3  bushels  more  corn  than  the  sulfate.  At  40  cents  a 
bushel  for  corn  the  kainit  has  paid  for  itself  the  first  year.  As  previ- 
ously stated,  kainit  contains  about  25  percent  of  potassium  sulfate 
together  with  some  magnesium  sulfate,  magnesium  chlorid,  and 
sodium  chlorid,  all  of  which  are  soluble  salts ;  and  the  results 
plainly  indicate  that  the  effects  produced  are  due  not  solely  to  the 
element  potassium,  but  in  part  at  least,  and  probably  in  large  part, 
to  the  stimulating  action  of  the  soluble  salt. 

In  this  connection  we  may  well  consider  results  obtained  s  at 
the  Rothamsted  Experiment  Station  in  England  where  wheat  has 
been  grown  on  the  same  land  every  year  for  56  years  with  dif- 
ferent kinds  of  soluble  salts  applied  to  different  parts  of  the  field. 
As  an  average  of  24  years  (from  1852  to  1875)  exactly  the  same 
increase  was  produced  (5.6  bushels)  whether  200*  pounds  of  po- 
tassium sulfate,  280*  pounds  of  magnesium  sulfate,  or  366^* 
pounds  of  sodium  sulfate  per  acre  per  annum  were  applied.  These 
results  are  not  altogether  conclusive  because  considerable  potas- 
sium salts  had  been  used  on  all  three  of  these  plots  previous  to  the 
beginning  of  this  24-year  test.  During  a  second  24  years  the  aver- 
age increases  produced  were  8.8  bushels  by  potassium  sulfate,  6.6 
bushels  by  magnesium  sulfate,  and  6.0  bushels  by  the  sodium  sul- 
fate, showing  that  while  the  soluble  salts  of  magnesium  and  so- 
dium produce  a  marked  effect,  the  potassium  salt  is  becoming  more 

*Approximately  molecular  proportions.  Excluding  water  of  crystallization 
the  amounts  applied  were  200  pounds  of  potassium  sulfate,  137  pounds  of  mag- 
nesium sulfate,  and  162  pounds  of  sodium  sulfate. 


THE  FERTILITY  IN  ILLINOIS  SOILS.  2l7 

effective  and  the  difference  of  2  or  2.8  bushels  may  be  attributed  to 
the  value  of  the  potassium  itself  as  plant  food.  It  may  be  said  that 
the  difference  was  much  greater  during  the  latter  part  of  the  second 
24-year  period  and  still  greater  subsequently.  In  1906  the  increase 
was  1 8.  i  bushels  by  potassium  sulfate,  7.8  bushels  by  magnesium 
sulfate,  and  7  bushels  by  sodium  sulfate,  the  potassium  salt  being 
now  more  than  twice  as  effective  as  the  other  salts. 

It  should  be  stated  that  in  the  experiments  reported  above  both 
at  Fairfield,  Illinois,  and  at  Rothamsted,  England,  the  soluble  salts 
were  applied  in  addition  to  phosphorus  and  the  yields  compared 
with  the  results  obtained  where  the  same  amounts  of  phosphorus 
were  applied  without  the  soluble  salts  mentioned.  Limestone  was 
also  provided  in  all  cases.  In  neither  case  was  farm  manure  applied 
and  the  soils  are  not  well  supplied  with  decaying  organic  matter, 
the  action  of  which  will  largely,  or,  if  provided  in  abundance,  en- 
tirely take  the  place  of  the  action  of  the  soluble  salts  as  such.  Ad- 
ditional experiments  on  the  Fairfield  field  include  an  equally  com- 
plete test  with  kainit  and  potassium  sulfate  on  land  to  which  8  tons 
per  acre  of  farm  manure  had  been  applied.  As  an  average  of  28 
tests  with  each  material  the  200  pounds  of  potassium  sulfate  in- 
creased the  yield  of  corn  by  2.9  bushels,  while  the  600  pounds  pf 
kainit  gave  3.3  bushels  increase,  as  compared  with  7  bushels  and 
i  o.i  bushels  increase,  respectively,  where  these  soluble  salts  were 
applied  in  the  absence  of  manure,  all  other  conditions  being  the 
same. 

Thus,  where  farm  manure  is  supplied  the  soluble  salts  produce 
but  little  effect  and  are  not  used  with  profit.  On  the  other  hand, 
phosphorus  produces  its  greatest  effect  when  used  in  connection  with 
organic  matter.  As  an  average  of  three  years  on  the  Fairfield  field 
rock  phosphate  and  limestone  in  addition  to  manure  have  produced 
1 2  bushels  more  corn  per  acre  than  has  been  produced  where  manure 
alone  was  used,  although  in  the  absence  of  either  decaying  organic 
matter  or  soluble  salts  the  phosphorus  produces  much  less  effect, 
especially  on  corn. 

In  Table  8  are  given  the  results  obtained  during  the  past  six 
ysars  on  the  DuBois  experiment  field  in  Washington  county.  In 
this  field  there  are  two -independent  series  of  ten  plots  each,  and 
the  crop  yields  reported  in  the  Table  are  in  all  cases  the  average 
from  two  plots  with  like  treatment. 

For  convenient  comparison  the  lower  part  of  Table  8  shows 
the  total  values  of  the  crops  produced  during  the  last  four  years  in 
this  four-year  rotation;  also  the  value  of  the  total  increase  and  of 
the  increase  above  that  produced  by  lime  alone. 


218  BULLETIN  No.  123.  [February, 

TABLE  8. — CROP  YIELDS  IN  SOIL  EXPERIMENTS:  DuBois  FIELD 


Graj  silt  loam  prairie 
Lower  Illinoisan  glaciation. 

Average  of  two  series  each  year, 
bushels  or  tons  per  acre. 

Soil  treatment  applied. 

Corn, 
1902. 

Oats, 
1903. 

Wheat, 
1904. 

Clover, 
1905. 

Corn, 
1906. 

Oats, 
1907. 

None  

4.9 
5.0 

13.3 
16.7 

4.8 
9.0 

1.27 
1.67 

31.4 
34.4 

16.0 
26.3 

Lime  

Lime,  nitrogen  

43 
10.0 
8.3 

19.4 
26.7 
27.4 

10.1 
26.7 
15.5 

1.79 

2.35 
2.19 

34.9 
34.2 
48.2 

34.1 
37.9 
41.8 

Lime,  phosphorus  

Lime,  potassium  

Lime,  nitrogen,  phosphorus  

8.7 
7.2 
13.3 

29.4 
25.5 
27.8 

32.0 
21.8 
29.9 

2.37 
2.43 
2.91 

31.4 
46.0 
52.1 

46.3 
41.5 
47.2 

Lime,  nitrogen,  potassium  

Lime,  phosphorus,  potassium  

Lime,  nitrogen  ,  phosphorus,  potassium 
Nitrogen,phosphorus,  potassium 

10.4 
3.4 

30.5 
29.4 

31.9 

27.8 

2.86 
2.69 

49.0 
45.3 

44.4 
36.1 

Value  of  Crops  per  acre  in  Four  Years,  1904, 1905,  1906,  1907. 


Soil  treatment  applied. 

Total  value  of 
four  crops. 

Value  of 

increase. 

None  

125  97 

Over 

34.82 

$  8.85 

lime 

Lime,  nitrogen  

38.66 

12.69 

$  3.84 

Lime,  phosphorus  

54.24 

28.27 

19.42 

Lime,  potassium  

51.31 

25.34 

16.49 

59.19 

33.22 

24.37 

Lime,  nitrogen,  potassium  

56.32 

30.35 

21.50 

Lime,  phosphorus,  potassium  

68.43 

42.46 

33.61 

Lime,nitrogen,phosphorus,potassium 
Nitrogen,  phosphorus,potassium 

67.74 
60.49 

41.77 
34.52 

32.92 

The  values  are  computed  at  35  cents  a  bushel  for  corn,  25  cents 
for  oats,  70  cents  for  wheat,  and  $6.00  a  ton  for  clover  hay.  Not 
only  are  these  prices  conservative,  but  the  quality  of  the  crops  from 
the  well  treated  plots  is  much  better  than  from  the  untreated  land, 
especially  for  wheat  and  clover. 

With  an  increase  of  $42.46  from  one  acre  of  land  in  four  years 
above  the  total  receipts  from  the  untreated  land  one  can  well  afford 
to  improve  the  soil.  Even  with  the  use  of  200  pounds  of  steamed 
bone  meal  at  $25  a  ton  and  100  pounds  of  potassium  sulfate  at  $50 
a  ton,  making  a  cost  of  $5.00  an  acre  a  year,  the  increase  has  paid 
the  cost  and  added  100  percent  profit  for  bone  meal  and  50  percent 
profit  for  the  potassium  used,  besides  leaving  in  the  soil  more  than 


THE  FERTILITY  IN  ILLINOIS  SOILS.  219 

half  of  the  phosphorus  applied  and   furnishing  clover  and  other 
large  crops  from  which  to  make  manure. 

From  all  data  and  information  thus  far  secured,  of  which  only 
a  few  average  and  trustworthy  illustrations  are  mentioned  in  this 
bulletin,  the  following  recommendations  are  made  for  the  improve- 
ment of  the  common  gray  silt  loam  prairie  land  of  the  Lower  Illi- 
noisan  glaciation : 

1.  Correct  the  acidity  of  the  soil  with  an  application  of  from  two 
to  five  tons  per  acre  of  ground  limestone,  best  applied  after  plowing 
in  the  summer  or  fall,  and  then  mixed  with  the  surface  soil  by  disk- 
ing or  harrowing  in  preparing  the  seed  bed  for  wheat  or  timothy 
where  clover  is  to  be  seeded  the  next  spring.     (See  Plates  3  and  4). 

2.  Adopt  a  good  crop  rotation  in  which  clover  or  mixed  clover 
and  timothy  shall  occupy  the  land  from  one-third  to  one-half  of 
the  time. 

3.  Increase  the  stock  of  phosphorus  in  the  soil  by  applying 
more  than  would  be  removed  in  large  crops.     An  application  of 
1000  pounds  per  acre  of  raw  rock  phosphate  every  five  or  six  years 
will  accomplish  this. 

4.  Increase  the  supply  of  active  humus,  or  decaying  organic 
matter,  by  pasturing  during  part  of  the  rotation  and  by  using  for 
feed  and  bedding  from  one-half  to  two-thirds  of  the  crops  har- 
vested, protecting  the  manure  from  exposure  and  loss  by  hauling 
directly  from  the  stall  and  spreading  with  the  phosphate  upon  the 
field  preferably  upon  the  new  meadows  or  old  pasture  land  to  be 
plowed  under  for  corn. 

5.  Where  it  is  impossible  at  first  to  apply  manure  or  to  turn 
under  liberal  amounts  of  organic  matter,  an  application  of  400  to 
600  pounds  per  acre  of  kainit  in  connection  with  the  phosphate  will 
help  to  grow  larger  crops  for  a  time  and  thus  increase  the  supply  of 
organic  matter  to  be  returned  in  stable  manure  and  by  pasturing, 
after  which  the  use  of  kainit  may  be  discontinued. 

The  experiments  now  being  conducted  on  this  type  of  soil  will 
ultimately  furnish  more  complete  information  as  to  the  effects  of 
different  crop  rotations,  of  the  continued  use  of  stable  manure, 
green  manures,  limestone,  phosphorus  in  different  forms,  potassium 
sulfate  and  kainit;  also  the  effect  and  practicability  of  subsoiling 
and  of  tile-drainage  with  the  tile  laid  at  different  depths  and  cov- 
ered with  different  materials,  as  with  earth  alone  and  also  with  a 
few  inches  of  straw  or  cinders  or  gravelly  sand  before  filling  in  with 
earth. 

The  results  of  these  investigations  will  be  published  from  time 
to  time  in  bulletins  or  circulars  which  will  be  sent  to  all  who  ask 
to  have  their  names  placed  upon  the  Experiment  Station  mail- 
ing list. 


220 


BULLETIN  No.  123. 


[February, 


PI.ATE  3. — CLOVER  (AND  CRAB  GRASS)  WITH  PHOSPHORUS  ONLY:  YIELD  1.05 
TONS:  EDGEWOOD  SOIL  EXPERIMENT  FIELD,  1905. 

Bulletin  99,  "Soil  Treatment  for  the  Lower  Illinois  Glaciation," 
and  Circular  1 10,  "Ground  Limestone  for  Acid  Soils,"  are  still 
available  and  will  be  sent  to  anyone  upon  request. 

For  more  details  concerning  the  chemical  composition  of  this 
and  other  types  of  soil,  see  the  appendix  to  this  bulletin,  and  for 
further  discussion  of  soil  acidity  see  under  the  heading  "yellow  silt 
loam"  in  the  following  pages. 

BROWN  SILT  LOAM  PRAIRIE  SOILS  (26) 

Brown  silt  loam  constitutes  the  most  common  prairie  soil  in 
the  Middle  and  Upper  Illinoisan,  Pre-Iowan,  and  Early  Wisconsin 
glaciations  and  is  found  to  some  extent  also  in  the  lowan  and  Late 
Wisconsin.  It  is  called  "the  ordinary  prairie  land"  by  farmers 
throughout  the  corn  belt,  extending  from  Coles,  northern  Macoupin, 
and  McDonough  counties  to  the  north  line  of  the  State. 

In  the  name  of  this  soil  type,  brown  silt  loam,  the  term  brown 
is  used  to  designate  about  the  same  color  as  when  used  to  describe 
a  brown  horse,  as  distinguished  from  a  black  soil  or  a  black  horse. 
The  soil  is  not  reddish  brown  or  chocolate.  It  is  dark  colored  but 


I90S.] 


THE  FERTILITY  IN  ILLINOIS  SOILS. 


221 


PLATE  4. — CLOVER  WITH  LJME  AND  PHOSPHORUS:  YIELD  2:10  TONS:  EDGE- 
WOOD  SOIL  EXPERIMENT  FIELD,  1905. 

not  a  genuine  black  under  normal  conditions,  although  when  wet 
the  darker  phase  of  the  type  appears  black. 

All  brown  silt  loams  are  given  the  soil  type  number  26,  to 
which  the  number  of  the  soil  area  is  prefixed  to  designate  the  indi- 
vidual soil,  as  426  for  the  Middle  Illinoisan  brown  silt  loam,  726 
for  the  lowan  brown  silt  loam,  etc.  Not  infrequently  the  brown 
silt  loam  extends  over  low  or  broad  moraines  as  well  as  over  the 
more  extensive  nearly  level  or  undulating  plains  between  the  mo- 
raines, but  only  one  number  is  used  for  the  type  within  a  single 
glaciation,  as  1126  for  the  Early  Wisconsin  in  which  the  type  is 
more  extensive  on  the  intermorainal  tracts,  and  1026  for  the  Late 
Wisconsin,  an  area  consisting  largely  of  broad  complex  moraines 
on  which  more  brown  silt  loam  is  found  than  on  the  smaller  areas 
between  the  moraines. 

While  the  different  brown  silt  loams  are  similar  in  many  re- 
spects, they  differ  somewhat  in  chemical  composition,  varying  with 
age  or  formation  of  the  different  areas,  and  it  is  noteworthy  that 
in  the  older  soil  areas  the  brown  silt  loam  is  either  no  longer  rep- 
resented (as  in  the  Lower  Illinoisan  glaciation)  or  it  is  replaced  to 


222  BULLETIN  No.  123.  [February, 

some  extent  by  a  type  of  soil  intermediate  in  character  and  value 
between  brown  silt  loam  and  gray  silt  loam  on  tight  clay.  This  in- 
termediate type  is  well  developed  in  places  in  the  southern  part  of 
the  Middle  Illinoisan  glaciation  and  in  the  western  part  of  the  Up- 
per Illinoisan,  but  if  is  only  one  of  many  minor  types  whose  exact 
location  and  investigation  will  be  reported  in  connection  with  the 
detail  soil  survey  by  counties. 

The  top  soil  of  the  brown  silt  loam  consists  of  a  friable  dark 
colored  and  fairly  uniform  soil  to  a  depth  of  16  to  20  inches  with 
appreciably  less  organic  matter  at  the  lower  depth.  Below  the  top 
soil  from  1 6  or  20  inches  to  40  inches  and  more,  is  the  yellow  silty 
subsoil,  somewhat  less  porous  or  friable  than  the  top  soil  but  not 
very  compact. 

This  soil  and  subsoil  have  great  capacity  to  absorb  and  retain 
water  from  heavy  rains  and  later  to  deliver  the  moisture  to  growing 
crops  as  needed.  In  other  words,  the  crops  growing  on  brown  silt 
loam  soils  are  enabled  to  withstand  drouths  that  would  produce 
very  severe  damage  on  such  a  soil  as  the  Lower  Illinoisan  gray  silt 
loam  on  tight  clay.  Of  course  even  the  brown  silt  loam  becomes 
much  less  absorbent  and  less  retentive  of  moisture  where  the  sur- 
face soil  is  allowed  to  become  deficient  in  humus.  ; 

In  Table  3  is  given  the  average  composition  of  the  surface  soil 
of  the  brown  silt  loam  in.  each  area.  In  nitrogen  the  brown  silt 
loam  of  the  Middle  Illinoisan  (426)  and  of  the  Pre-Iowan  (626) 
is  below  the  average.  The  former  is  the  oldest  and  the  latter  the 
most  rolling  of  the  six  brown  silt  loam  areas,  which  may  account 
for  these  lower  averages.  The  phosphorus  varies  somewhat  in  har- 
mony with  the  variation  in  nitrogen,  except  in  the  Early  Wisconsin 
area.  The  Late  Wisconsin  brown  silt  loam  (1026)  is  the  most 
recent  and  also  the  richest  in  nitrogen,  phosphorus,  and  potassium. 

In  the  Pre-Iowan  and  lowan  glaciations  the  brown  silt  loam  is 
commonly  somewhat  sour,  the  acidity  being  more  marked  in  the 
subsurface  and  subsoil  than  in  the  surface,  as  is  usually  the  case 
with  strongly  acid  soils  (see  appendix  for  details).  The  principal 
type  of  upland  soil  in  the  lowan  glaciation  is  a  sandy  loam  (760), 
further  described  in  the  following'  pages.  The  fact  that  the  Pre- 
Iowan  and  lowan  brown  silt  loams  contain  more  fine  sand  than  is 
found  in  this  type  in  other  glaciations  suggests  that  the  higher 
acidity  in  these  two  areas  may  be  due  to  an  original  deficiency  in 
lime,  the  loessial  deposit  having  been  modified  by  the  sandy  ma- 
terial which  is  so  commonly  exposed  and  which  must  have  contrib- 
uted more  or  less  to  the  glacial  drift  from  which  the  loess  was 
probably  derived  as  already  explained. 


ipo8.]  THE  FERTILITY  IN  ILLINOIS  SOILS.  223 

As  a  general  average  (the  Late  Wisconsin  being  disregarded) 
the  brown  silt  loams  contain  in  the  surface  soil  of  an  acre  about 
4800  pounds  of  nitrogen,  1200  pounds  of  phosphorus,  and  34,000 
pounds  of  potassium,  amounts  which,  if  they  could  be  drawn  upon 
at  will,  would  furnish  the  nitrogen  for  100  bushels  of  corn  (grain 
only)  every  year  for  48  years,  the  phosphorus  for  70  years,  or  the 
potassium  for  1790  years.  For  four -tons  per  acre  of  clover  hay 
each  year,  the  nitrogen,  if  drawn  only  from  the  surface  soil,  would 
be  sufficient  for  30  years,  the  phosphorus  for  60  years,  and  the 
potassium  for  280  years. 

These  data  are  for  very  large  crops,  and  take  into  account  only 
the  plant  food  in  the  surface  soil  to  a  depth  of  seven  inches  but 
these  crops  are  not  too  large  to  try  to  raise  and  the  fertility  of  the 
surface  soil  must  be  maintained  if  we  are  to  maintain  a  permanent 
profitable  agriculture.  We  may  reduce  the  crop  yields  to  the  low- 
est limit  of  profit  on  land  valued  at  $150  to  $200  an  acre,  but  still 
the  absolute  limit  in  years  is  short  for  the  nitrogen  and  phosphorus 
in  this  most  common  Illinois  prairie  soil ;  and,  if  such  crops  of  corn 
and  clover  as  are  mentioned  above  had  been  removed  from  this 
land  from  the  time  Columbus  discovered  America  until  now,  every 
pound  of  phosphorus  contained  in  the  soil  to  a  depth  of  four  feet 
would  have  been  required  for  the  crops  grown. 

Nitrogen  can,  of  course,  be  secured  from  the  air  by  means  of 
clover  and  other  legumes,  but  on  any  land  capable  of  producing  40 
or  50'  bushels  of  corn  per  acre  the  soil  will  furnish  as  much  nitrogen 
to  the  clover  crop  as  will  remain  in  the  roots  and  stubble  after  the 
hay  and  seed  crops  are  removed.  In  other  words,  to  enrich  such 
soil  in  nitrogen  the  clover  crop  must  be  returned  to  the  land,  either 
directly  or  in  manure.  The  amount  of  clover  necessary  to  be 
plowed  under  in  order  to  furnish  sufficient  nitrogen  to  meet  the 
needs  of  the  grain  or  grass  crops  to  be  grown  in  the  rotation  can 
easily  be  computed  from  Table  i,  and  every  farmer  should  make 
such  computation  for  his  rotation. 

On  the  ordinary  Early  Wisconsin  brown  silt  loam  on  the  Uni- 
versity soil  experiment  field  at  Urbana,  a  three-year  rotation  of 
corn,  oats,  and  clover  is  practiced  on  three  fields  so  that  every  crop 
is  grown  every  year.  As  an  average  of  the  last  three  years,  includ- 
ing three  crops  of  corn,  three  of  oats,  and  three  of  clover,  the  yields 
per  acre  have  been  72  bushels  of  corn,  59  bushels  of  oats,  and  .89 
ton  of  air-dry  clover  hay  where  no  phosphorus  has  been  applied; 
but  where  phosphorus  has  been  applied  on  similar  land  in  the  same 
fields  the  average  yields  have  been  90  bushels  of  corn,  71  bushels 
of  oats,  and  1.78  tons  of  air-dry  hay.  (See  Plates  5  and  6). 


224 


BULLETIN  No.  123. 


[February, 


PLATE  5.— CLOVER  AFTER  OATS  WITH  L,IME  TREATMENT:  YIELD  .87  TON: 
URBANA  SOIL  EXPERIMENT  FIELD,  1905. 

At  35  cents  a  bushel  for  corn,  25  cents  for  oats,  and  $6.00  a 
ton  for  hay,  the  value  of  the  increase  produced  by  the  phosphorus 
is  twice  the  cost  of  the  phosphorus  applied  in  the  form  of  steamed 
bone  meal,  a  form  in  which  phosphorus  costs  nearly  three  times  as 
much  as  in  raw  rock  phosphate  (see  Table  2).  Furthermore,  the 
land  to  which  no  phosphorus  was  applied  has  lost  30  pounds  of 
phosphorus  per  acre  in  the  crops  removed,  while,  the  bone  meal  ap- 
plied contained  35  pounds  more  phosphorus  than  was  removed  in 
the  three  larger  crops. 

Where  both  bone  meal  and  manure  have  been  applied  the  aver- 
age yield  of  corn  was  93  bushels,  and  where  potassium  also  has 
been  applied  in  addition  to  the  manure  and  phosphorus,  the  yield 
has  been  96  bushels  of  corn,  as  a  three-year  average. 

As  a  rule  potassium  is  of  little  benefit  on  the  brown  silt  loams, 
and  not  infrequently  it  reduces  the  crop  yields.  With  two  tests  each 
year  on  each  crop  potassium  produced  an  average  increase  of  3 
bushels  of  corn  and  .16  ton  of  hay,  but  decreased  the  yield  of  oats 
by  2  bushels. 

Table  9  gives  results  obtained  during  the  past  six  years  from 
the  Sibley  soil  experiment  field,  located  in  Ford  county  on  typical 
brown  silt  loam  prairie  of  the  Illinois  corn  belt. 


1908.] 


THE  FERTILITY  IN  ILLINOIS  SOILS. 


PLATE  6. — CLOVER  AFTER  OATS  WITH  L/IME  AND  PHOSPHORUS  TREATMENT: 
YIELD  1:83  TONS:  URBAN  A  SOIL  EXPERIMENT  FIELD,  1905. 

Table  9  is  so  easily  understood  that  it  is  not  necessary  to  take 
space  here  for  a  complete  discussion  of  the  data. 

Previous  to  1902  this  land  had  been  cropped  with  corn  and  oats 
for  many  years  under  a  system  of  tenant  farming  and  the  soil  had 
become  somewhat  deficient  in  active  humus.  While  phosphorus  was 
the  limiting  element  of  plant  food,  the  supply  of  nitrogen  becoming 
available  annually  was  but  little  in  excess  of  the  phosphorus,  as  is 
well  shown  by  the  corn  yields  for  1903  when  phosphorus  produced 
an  increase  of  8  bushels,  nitrogen  without  phosphorus  produced  no 
increase,  but  nitrogen  and  phosphorus  increased  the  yield  by  15 
bushels. 

After  six  years  of  additional  cropping,  however,  nitrogen  ap- 
pears to  have  become  the  most  limiting  element,  the  increase  in 
1907  being  9  bushels  from  nitrogen  and  only  5  bushels  from  phos- 
phorus, while  both  together  produced  an  increase  of  33  bushels  of 
corn.  By  comparing  the  corn  yields  for  the  four  years,  1902,  1903, 
1906,  and  1907,  it  will  be  seen  that  the  untreated  land  has  appar- 
ently grown  less  productive,  whereas  on  land  receiving  both  phos- 
phorus and  nitrogen  the  yield  has  appreciably  increased,  so  that  in 
1907  when  the  untreated  rotated  land  produced  only  34  bushels  of 
corn  per  acre,  a  yield  of  72  bushels,  or  more  than  twice  as  much, 
was  produced  where  lime,  nitrogen,  and  phosphorus  had  been  ap- 


226 


BULLETIN  No.  123. 


[February, 


plied,  although  these  two  plots  produced  exactly  the  same  yield  (57 
bushels)  in  1902.  While  the  actual  yields  might  be  quite  different 
under  different  seasonal  conditions,  the  relative  and  increasing  dif- 
ferences between  the  plots  must  be  considered  as  representative  and 
due  to  the  difference  in  soil  treatment. 

TABLE  9.— CROP  YIELDS  IN  Sou,  EXPERIMENTS: — SIBLEY  FIELD 


Brown  silt  loam  prairie 
Early  Wisconsin  glaciation. 

Corn, 
1902. 

Corn,      Oats, 
1903.        1904. 

Wheat, 

1905. 

Corn, 

1906. 

Corn, 
1907. 

Plot. 

Soil  treatment  applied. 

Bushels  per  acre. 

101 
102 

None  

57.3     50.4 
60.0      54.0 

74.4 
74.7 

29.5 
31.7 

36.7 
39.2 

33.9 
38.9 

Lame  

103 
104 
105 

Lime,  nitrogen  

60.0 
61.3 
56.0 

54.3 
62.3 
49.9 

77.5 
92.5 
74.4 

32.8 
36.3 
30.2 

41.7 
44.8 
37.5 

48.1 
43.5 
34.9. 

Lime,  phosphorus  

Lime,  potassium  

106 

107 
108 

Lime,  nitrogen,  phosphorus  .  .  . 
Lime,  nitrogen,  potassium  
Lime,  phosphorus,  potassium.  . 

57.3 
53.3 
58.7 

69.1 
51.4 
60.9 

88.4 
75.9 
80.0 

45.2 
37.7 
39.8 

68.5 
39.7 
41.5 

72.3 
51.1 
39.8 

109 
110 

Lime,  nitrogen,  phosphorus, 
potassium  

58.7 
60.0 

65.9 
60.1 

82.5 
85.0 

48.0 

48.5 

69.5 
63.3 

80.1 

72.3 

Nitrogen,  phosphorus, 
potassium  

Value  of  Crops  per  acre  in  Six  Years. 


Plot. 

Soil  treatment  applied. 

Total  value 
of  six  crops. 

Value  of 

increase. 

101 

None  

$101  .  66 

Over 

102 

Lime  

108.11 

$6.45 

lime. 

103 

Lime,  nitrogen   

113.78 

12.12 

$5.67 

104 

Lime,  phosphorus  

122.71 

21.05 

14.60 

105 

Lime,  potassium  

102.15 

.49 

-5.92 

106 
107 
108 

Lime,  nitrogen,  phosphorus  .  .  . 
Lime,  nitrogen,  potassium  
Lime,  phosphorus,  potassium.  . 

147.26 
113.80 
118.18 

45.64 
12.14 
16.56 

39.19 
5.69 
10.11 

109 

Lime,  nitrogen,  phosphorus, 
potassium  

150.20 

48.58 

42.13 

110 

Nitrogen,  phosphorus, 
potassium.  

144.70 

43.08 



In  the  lower  part  of  Table  9  are  shown  the  total  values  per  acre 
of  the  six  crops  from  each  of  the  ten  different  plots,  the  amounts 
varying  from  $101.62  to  $150.20;  also  the  value  of  the  increase 
produced ;  first,  above  the  untreated  land ;  and,  second,  above  the 
treatment  with  lime  alone,  corn  being  valued  at  35  cents  a  bushel, 
oats  at  25  cents,  and  wheat  at  70  cents. 


/po<?.]  THE  FERTILITY  IN  ILLINOIS  SOILS.  227 

Phosphorus  without  nitrogen  produced  $14.63  in  addition  to 
the  increase  by  lime,  and  with  nitrogen  phosphorus  produced  $33.49 
in  addition  to  the  increase  by  lime  and  nitrogen,  the  principal  part 
of  these  increases  having  been  made  during  the  later  years. 

The  results  show  that  in  17  cases  out  of  24  the  addition  of  po- 
tassium decreased  the  crop  yields. 

By  comparing  plots  101  and  102,  and  also  109  and  no,  it  will 
be  seen  that  the  average  increase  by  lime  was  about  $6.00,  or  $1.00 
an  acre  a  year,  suggesting  that  the  time  is  near  when  lime  also  must 
be  applied  to  these  brown  silt  loam  soils  (see  appendix). 

Because  of  the  tremendous  importance  of  this  most  common 
soil  type  to  Illinois  agriculture  and  to  the  prosperity  of  the  state, 
space  is  taken  to  insert  Table  10  giving  all  of  the  results  thus  far 
obtained  from  the  Bloomington  soil  experiment  field,  which  is  also 
located  on  the  brown  silt  loam  prairie  of  the  Illinois  corn  belt. 

The  general  results  of  the  six  years'  work  on  the  Bloomington 
field  tell  the  same  story  as  those  from  the  Sibley  field.  The  rota- 
tions differed  by  the  use  of  clover  and  cowpeas  in  1906,  and  in 
discontinuing  the  use  of  commercial  nitrogen  after  1905,  on  the 
Bloomington  field,  in  consequence  of  which  phosphorus  without 
nitrogen  (Plot  104)  produced  nearly  as  large  an  increase  ($29.42) 
as  the  increase  ($29.92)  by  phosphorus  with  nitrogen  (Plot  106)  ; 
whereas  on  the  Sibley  field  phosphorus  with  nitrogen  (Plot  106) 
produced  more  than  twice  as  large  an  increase  ($33.49)  as  the  in- 
crease ($14.63)  by  phosphorus  without  nitrogen. 

It  should  be  stated  that  a  draw  runs  near  plot  no  on  the  Bloom- 
ington field  and  the  crops  on  that  plot  are  sometimes  damaged  by 
overflow  or  imperfect  drainage  as  in  1903,  1904,  and  1907;  also 
that  in  1902  the  stand  of  corn  on  the  Bloomington  field  was  poor, 
though  fairly  uniform.  Otherwise  all  results  reported  in  Tables  9 
and  10,  including  more  than  100  tests,  are  considered  reliable,  and 
they  furnish  much  information  and  afford  many  very  interesting 
and  instructive  comparisons,  as  for  example  between  Plots  104 
and  1 06  and  between  108  and  109  on  the  Sibley  field  where  no 
legumes  are  grown  in  the  rotation;  also,  between  plots  103  and  106 
and  between  107  and  109  on  both  fields. 

Wherever  nitrogen  was  provided  either  by  direct  application  or 
by  the  use  of  legume  crops,  the  addition  of  the  element  phosphorus 
produced  very  marked  increases,  the  average  value  being  $33.31 
for  the  six  years,  or  $5.55  an  acre  a  year.  This  is  more  than  double 
its  cost  in  steamed  bone  meal,  the  form  in  which  it  was  applied  to 
these  fields.  On  the  other  hand,  the  use  of  phosphorus  without  ni- 
trogen will  not  maintain  the  fertility  of  the  soil  (see  Plots  104  and 


228 


BULLETIN  No.  123. 


[February, 


1 06,  Sibley  field),  and  a  liberal  use  of  clover  or  other  legumes  is 
suggested  as  the  only  practical  and  profitable  method  of  supplying 
the  nitrogen,  the  clover  to  be  plowed  under,  either  directly  or  as 
manure,  preferably  in  connection  with  the  phosphorus  applied,  es- 
pecially if  raw  rock  phosphate  is  used. 

TABLE  10.— CROP  YIELDS  IN  SOIL  EXPERIMENTS:  BLOOMINGTON  FIELD 


Brown  silt  loam  prairie 
Early  Wisconsin  glaciation. 

Corn, 
1902. 

Corn, 
1903. 

Oats, 
1904. 

Wheat, 
1905. 

Clover, 
1906. 

Corn 
1907 

Plot. 

Soil  treatment  applied. 

Bushels  or  tons  per  acre. 

101 
102 

None  

30.8 
37.0 

63.9 
60.3 

54.8 
60.8 

30.8 
28.8 

.39 
.58 

60.8 
63.1 

Li  nu-  

103 
104 
105 

Lime,  nitrogen  

35.1 
41.7 
37.7 

59.5 
73.0 
56.4 

69.8 

72.7 
62.5 

30.5 
39.2 
33.2 

.46 
1.65 
.51 

64.3 
82.1 
64.1 

Lime   phosphorus  

Lime,  potassium  

106 
107 
108 

Lime,  nitrogen,  phosphorus  .  .  . 
Lime,  nitrogen,  potassium  

43.9 
40.4 
50.1 

77.6 
58.9 
74.8 

85.3 
66.4 
70.3 

50.9 
29.5 
37.8 

* 

".81 
2.36 

78.9 
64.3 
81.4 

Lime,  phosphorus,  potassium.. 

109 
110 

Lime,  nitrogen,  phosphorus, 
potassium  

52.7 
52.3 

80.9 
73.1 

90.5 
71.4 

51.9 
51.1 

t  _* 
* 

88.4 
78.0 

Nitrogen,  phosphorus, 
potassium  

Value  of  Crops  per  acre  in  Six  Years. 


Plot. 

Soil  treatment  applied. 

Total  value 
of  six  crops. 

Value  of  increase. 

101 
102 

$92.03 
94.98 

$2  '.95 

Over 
lime. 

Lime  

103 
104 
105 

Lime,  nitrogen  

97.18 
124.40 
97.30 

5.15 
32.37 

5.27 

$2.20 
29.42 
2.32 

Lime,  phosphorus  

Lime,  potassium  

106 
107 
108 

Lime,  nitrogen,  phosphorus  .  .  . 
Lime,  nitrogen,  potassium  .... 
Lime,  phosphorus,  potassium.. 

127.10 
99.37 
130.41 

35.07 
7.34 
38.38 

32.12 
4.39 
35.43 

109 

110 

Lime,  nitrogen,  phosphorus, 
potassium  

136.66 
124.81 

44.63 

32.78 

41.68 

Nitrogen,  phosphorus, 
tjotassium  .  . 

*Clover  smothered  out  by  previous  very  heavy  wheat  crop. 

After  the  clover  hay  was  harvested  all  ten  of  the  plots  were  seeded  to 
cowpeas  and  the  crop  was  plowed  under  later  on  all  plots  as  green  manure 
for  the  1907  corn  crop. 

From  the  best  treated  plots  90  pounds  per  acre  of  phosphorus 
have  been  removed  from  the  soil  in  the  six  crops.    This  is  equal  to 
percent  of  the  total  phosphorus  contained  in  the  surface  soil  of 


/pa?.]  THE  FERTILITY  IN  ILLINOIS  SOILS.  229 

an  acre.  In  other  words,  if  such  crops  could  be  grown  for  80  years 
they  would  require  as  much  phosphorus  as  the  total  supply  in  the 
surface  7  inches  of  soil.  The  results  plainly  show,  however,  that 
without  the  addition  of  phosphorus  such  crops  cannot  be  grown 
year  after  year.  Where  no  phosphorus  was  applied  the  crops  re- 
moved only  70  pounds  of  phosphorus  in  six  years,  or  nearly  12 
pounds  a  year,  equivalent  to  almost  I  percent  of  the  total  amount 
(1200  pounds)  in  the  surface  soil. 

The  Auburn  soil  experiment  field  in  Sangamon  county  is  located 
on  typical  Middle  Illinoisan  brown  silt  loam  (426).  On  that  field 
phosphorus  is  applied  in  the  form  of  raw  rock  phosphate,  the  ini- 
tial application  being  one  ton  to  the  acre.  A  four-year  rotation  is 
practiced  consisting  of  corn  for  two  years  followed  by  oats  the 
third  year  and  clover  the  fourth  year.  There  are  two  independent 
series  of  plots  and  during  the  three  years  since  the  field  was  estab- 
lished three  crops  of  corn  and  one  of  oats  have  been  produced.  In 
each  series  there  are  four  plots  treated  with  phosphorus  and  four 
others  not  treated  with  phosphorus,  but  in  other  respects  they  are 
treated  alike.  As  an  average  of  these  four  tests  the  rock  phosphate 
increased  the  yield  of  corn  by  7  bushels  in  1905,  by  i  bushel  in 
1906,  and  by  8  bushels  in  1907,  and  increased' the  yield  of  oats  by 
8  bushels  in  1907. 

For  the  1905  crop  the  phosphorus  was  applied  and  plozved  down 
with  a  small  growth  of  clover  seeded  with  the  previous  oat  crop, 
but  for  the  1906  crop  the  phosphorus  may  have  been  plowed  up  by 
deeper  plowing,  and  if  so  it  was  probably  chiefly  in  the  two  or  three 
inches  of  surface  soil  where  the  corn  roots  do  not  feed  appreciably, 
and  this  may  account  for  its  smaller  effect  for  that  season.  Some 
other  similar  results  under  similar  circumstances  support  this  sug- 
gestion. Ultimately,  of  course,  by  repeated  plowing,  disking,  etc., 
the  rock  phosphate  will  become  well  mixed  with  the  plowed  soil. 

The  Galesburg  soil  experiment  field,  located  in  Knox  county 
on  the  Warren  county  line  on  typical  Upper  Illinoisan  brown  silt 
loam  (526),  has  been  in  operation  four  years.  A  six-year  rotation 
has  been  begun  consisting  of  two  years  in  corn,  oats  the  third  year, 
wheat  the  fourth  year,  and  clover  and  timothy  meadow  the  fifth 
and  sixth  years.  It  is  absurd,  of  course,  to  expect  anything  like 
complete  information  as  to  the  effects  of  soil  treatment  in  connec- 
tion with  this  crop  rotation  at  this  date.  The  first  six  years  will  be 
required  to  get  the  rotation  properly  underway  and  must  be  con- 
sidered as  a  preliminary  period.  The  second  six  years  should  fur- 
nish some  reliable  indications  as  to  the  probable  effect  of  the  dif- 
ferent systems,  and  after  that  period  definite  and  conclusive  infor- 
mation should  accumulate  rapidly. 


230  BULLETIN  No.  123.  [February, 

There  are  three  independent  series  of  plots  in  this  field,  of  which 
one  grows  corn  for  two  years,  another  grows  oats  one  year  and 
wheat  the  next,  while  the  third  grows  mixed  clover  and  timothy 
during  the  same  two  years,  and  the  rotation  is  continued  as  given 
above.  On  series  100  corn  was  grown  in  1904  and  1905,  oats  in 
1906,  and  wheat  in  1907,  clover  and  timothy  having  been  seeded 
for  1908  and  1909.  On  the  200  series  oats  were  grown  (on  sod 
ground)  in  1904,  wheat  in  1905,  and  mixed  clover  and  timothy  in 
1906  and  1907.  Series  300  was  left  in  meadow  for  1904  and  1905, 
and  then  cropped  with  corn  in  1906  and  1907. 

By  using  the  corn,  oats,  and  wheat  data  from  the  100  series 
for  the  four  years,  the  clover  and  timothy  data  from  the  200  series, 
and  the  corn  data  from  the  300  series,  we  have  some  preliminary 
results  for  each  of  the  six  crops  comprising  the^  rotation.  As  an 
average  of  four  tests  with  and  without  phosphorus  (8  tests  for 
each  corn  crop)  the  raw  rock  phosphate  used  on  this  field  increased 
the  yield  of  first-year  corn  by  5.5  bushels  and  of  second-year  corn 
by  9.3  bushels,  increased  the  yield  of  oats  by  3.6  bushels  in  1906 
and  wheat  by  5.1  bushels  in  1907,  and  increased  the  yield  of  hay  by 
.26  ton  in  1906  and  by  .53  ton  in  1907.  At  the  prices  previously 
mentioned  the  increase  in  these  six  crops  is  worth  $14.40  per  acre. 

The  initial  application  of  rock  phosphate  was  il/>  tons  per  acre 
for  the  six-year  rotation  and  this  application  is  to  be  repeated  for 
the  second,  and  possibly  for  the  third  and  fourth,  rotations,  after 
which  1000  pounds  of  rock  phosphate  are  to  be  applied  every  six 
years.  At  $8.00  for  the  12^  percent  rock  phosphate  in  carload  lots, 
the  1 l/2  tons  cost  $12.00  and  added  to  the  soil  375  pounds  of  the 
element  phosphorus,  of  \vhich  the  six  crops  on  treated  land  removed 
about  68  pounds,  leaving  the  soil  richer  in  phosphorus  by  307 
pounds  than  at  the  beginning.  At  this  rate  this  system  will  increase 
the  phosphorus  content  of  the  plowed  soil  from  1160  pounds  (the 
average  of  the  Galesburg  field  in  1904)  to  nearly  1500  pounds  in 
1910,  and  to  1800  pounds  (an  increase  of  50  percent)  in  1916,  and, 
if  continued,  to  2100  pounds  per  acre  in  1922,  and  to  2400  pounds 
(double  the  original  content)  in  1928. 

On  the  other  hand  it  should  be  kept  in  mind  that  the  six  crops 
harvested  from  the  untreated  land  left  .the  soil  poorer  in  phosphorus 
by  56  pounds  per  acre,  which  is  5  percent  of  the  phosphorus  present 
in  the  surface  soil.  While  it  is  to  be  taken  for  granted  that  some 
part  of  this  came  from  the  subsurface  and  subsoil,  the  fact  still  re- 
mains that  phosphorus  is  already  so  deficient  in  this  soil  as  to  limit 
the  crop  yields,  and  we  may  well  ask  ourselves  the  question  \vhether 
we  shall  continue  to  reduce  the  productive  power  of  the  soil  toward 


/pa?.]  THE  FERTILITY  IN  ILLINOIS  SOILS.  231 

ultimate  land  ruin,  and  thus  become  the  curse  of  our  own  grand- 
children or  their  children,  or  whether  we  shall  adopt  a  system 
which  assures  even  greater  profits  to  ourselves  and  a  richer  soil  as 
a  heritage  to  our  children,  and  greater  future  prosperity  to  the 
commonwealth  of  Illinois. 

The  Myrtle  soil  experiment  field  in  Ogle  county  is  located  on 
the  Pre-Iowan  brown  silt  loam  (626).  Apparently  phosphorus  and 
nitrogen  are  about  equally  deficient.  The  experiments  have  been 
in  progress  for  four  years.  Where  rock  phosphate  was  applied  at 
the  rate  of  I  ton  per  acre  for  the  initial  application,  with  no  adequate 
supply  of  decaying  organic  matter  in  the  soil,  but  little  effect  has 
appeared  in  the  grain  crops,  the  average  increase  being  2.5  bushels 
per  acre  of  corn  and  1.6  bushels  of  oats. 

With  the  clover  crop,  however,  which  it  should  be  remembered 
need  not  be  limited  in  yield  because  of  any  deficiency  of  soil  nitro- 
gen, having  power  to  secure  from  the  air  nitrogen  to  supplement  so 
far  as  necessary  the  soil's  available  supply,  the  effect  of  phosphorus 
has  already  been  marked,  the  increase  of  air-dry  clover  hay  as  an 
average  of  four  tests  each  year  being  .22  ton  for  1906  and  .63  ton 
for  1907.  With  the  increased  amount  of  clover  residues  and  with 
the  increased  amount  of  manure  to  be  made  from  the  larger  yield 
of  clover  hay  and  with  the  help  of  this  decaying  organic  matter  to 
liberate  more  phosphorus  from  the  rock  phosphate  applied,  in- 
creased crops  of  corn  and  other  grains  must  follow  on  this  field  as 
they  have  on  others. 

No  soil  experiment  fields  have  yet  been  established  on  the  lowan 
brown  silt  loam  (726)  nor  on  the  Late  Wisconsin  brown  silt  loam 
(1026).  Results  similar  to  those  reported  for  this  type  in  other 
areas  are  to  be  expected  in  those  areas,  except  that  they  will  prob- 
ably be  less  marked  in  the  Late  Wisconsin,  especially  on  the  better 
phase  of  the  type,  because  of  the  higher  percentages  of  both  phos- 
phorus and  nitrogen  in  the  brown  silt  loam  of  that  area. 

Additional  soil  experiment  fields  are  greatly  needed,  and  will  be 
established  as  soon  as  sufficient  funds  are  provided,  not  only  on 
these  most  important  soil  types  but  also  on  several  other  more  local 
and  less  extensive  types,  and  not  only  for  purposes  of  investigation 
but  also  to  serve  for  demonstration  and  definite  object  lessons 
where  farmers  and  landowners  may  see  for  themselves  the  results 
produced  by  the  best  and  most  profitable  practice  in  soil  improve- 
ment looking  toward  permanent  systems  of  agriculture  for  the 
state,  and  conducted  on  soil  types  which  they  will  be  able  to  recog- 
nize on  their  own  farms. 


232  BULLETIN  No.  123.  [February, 

RECOMMENDATIONS  FOR  BROWN  SILT  LOAM  PRAIRIE  SOILS 

The  information  thus  far  secured  is  too  meager  to  justify  rec- 
ommendations concerning  many  important  problems  relating  to 
methods  and  systems  of  farming  on  the  brown  silt  loam  prairie 
soils,  but  two  principles  are  already  well  established. 

First,  we  must  maintain  or  increase  the  supply  of  decaying  or- 
ganic matter  in  the  soil,  by  means  of  crop  rotations  and  the  use  of 
animal  manures  and  green  manures.  A  six-year  rotation  (similar 
to  that  on  the  Galesburg  field)  in  which  grain  crops  are  grown  for 
three  or  four  years  followed  by  mixed  clover  and  timothy  for  two 
or  three  years  in  meadow  and  pasture,  with  about  two-thirds  of  the 
total  crops  fed  on  the  farm  and  all  manure  carefully  saved  and  re- 
turned to  the  land,  will  certainly  be  approaching  toward  a  perma- 
nent system  for  maintaining  a  sufficient  supply  of  humus  in  the 
soil,  as  compared  with  the  present  most  common  soil-exhausting 
practice  of  growing  from  two  to  five  crops  of  corn  in  succession, 
burning  the  stalks  each  year,  and  then  substituting  oats  for  one 
year,  possibly  with  some  clover  seeded  in  the  oats  to  be  plowed  un- 
der either  the  same  fall  or  the  next  spring  with  a  feeling  that  the 
land  has  been  fertilized  enough  for  three  or  four  more  corn  crops. 

Second,  we  must  return  to  the  soil  in  some  form  at  least  as 
much  phosphorus  as  we  remove  in  crops,  and  the  weight  of  evidence 
thus  far  secured  from  properly  conducted  investigations  is  clearly 
in  favor  of  using  liberal  amounts  of  fine-ground  raw  rock  phos- 
phate, with  the  full  understanding  that  abundance  of  decaying  or- 
ganic matter  is  to  be  provided  to  assist  in 'making  the  phosphorus 
soluble  and  available  for  growing  crops. 

To  provide  for  as  large  crop  yields  as  we  ought  to  try  to  produce 
will  require  an  application  of  25  pounds  of  phosphorus  per  acre  for 
each  year  in  the  rotation,  preferably  spread  on  the  field  at  one  time 
and  plowed  under  with  manure  or  other  organic  matter.  The 
phosphorus  content  of  the  manure  applied  may  of  course  be  consid- 
ered a  part  of  the  required  amount.  To  increase  the  total  amount 
of  phosphorus  in  the  surface  soil  to  2000  pounds  per  acre  would 
require  heavier  applications  for  a  few  years.  Three  tons  of  rock 
phosphate  containing  12^2  percent  of  the  element  would  add  750 
pounds  of  phosphorus,  and  would  cost  at  present  prices  from  $25 
to  $30.  This  would  raise  the  phosphorus  content  of  the  soil  from 
1200  pounds,  the  present  average,  to  1950  pounds.  To  determine 
whether  it  will  be  profitable  to  increase  still  further  the  total  stock 
of  phosphorus  in  the  surface  soil  requires  further  investigation.  The 


THE  FERTILITY  IN  ILLINOIS  SOILS.  233 

750  pounds  suggested  above  would  equal  the  phosphorus  required 
for  100  bushels  of  corn  (grain  only)  every  year  for  44  years,  or  for 
44  bushels  (about  the  present  average  yield  for  the  Illinois  corn 
belt)  every  year  for  100  years.  In  other  words  the  man  who  in- 
creases the  phosphorus  content  of  his  soil  by  750  pounds  provides 
the  only  element  that  need  be  purchased  sufficient  to  meet  the  needs 
of  the  present  average  yields  for  another  one  hundred  years,  and  at 
present  prices  for  corn  and  rock  phosphate  the  expense  for  such  an 
application  is  no  more  than  the  value  of  one  7o-bushel  crop  of  corn. 

It  is  very  evident  from  the  information  already  secured  that  we 
can  thus  not  only  increase  the  phosphorus  content  of  the  surface 
soil  by  more  than  one-half  of  our  present  stock,  but  also  that  the 
increase  in  crop  yields  in  a  proper  system  of  farming  will  pay  for 
such  applications  in  a  few  years. 

Further  data  are  required,  and  are  accumulating,  concerning 
the  effect  of  lime  on  the  brown  silt  loams.  As  mentioned  above  the 
composition  of  this  type  in  the  Pre-Iowan  and  lowan  glaciations 
indicates  that  the  use  of  limestone  may  be  advisable  and  profitable 
in  those  areas.  In  the  Middle  and  Upper  Illinoisan  and  Early  Wis- 
consin glaciations  the  supply  of  limestone  in  the  brown  silt  loam  is 
frequently  already  exhausted  and  on  some  fields  very  appreciable 
effects  have  followed  its  application. 

For  a  more  complete  discussion  of  the  effect  of  crop  rotations, 
the  value,  and  methods  of  increasing  the  value,  of  farm  manure, 
and  for  additional  data  relating  to  soil  improvement  and  the  com- 
parative value  of  different  forms  of  phosphorus,  Illinois  readers  are 
referred  to  Circular  96,  "Soil  Improvement  for  the  Illinois  Corn 
Belt,"  and  to  Circular  108,  "Illinois  Soils  in  Relation  to  Systems  of 
Permanent  Agriculture,"  which  will  be  furnished  free  of  charge 
upon  request. 

BLACK  CLAY  LOAM  PRAIRIE  SOILS  (20) 

The  commonest  type  of  soil  on  the  very  flat  prairie  lands  of  the 
corn  belt  is  black  clay  loam.  As  indicated  by  the  name,  it  is  black 
in  color,  clayey,  or  sticky  and  plastic,  in  texture,  and  rich  in  organic 
matter.  It  is  commonly  known  as  the  heavy  black  prairie  soil,  and 
is  sometimes  called  black  gumbo  land. 

It  is  most  abundant  in  the  broad  intermorainal  tracts  in  the 
Early  Wisconsin  glaciation  where  it  represents  the  richest  Illinois 
prairie  land  existing  in  large  area,  containing  as  an  average  in  two 
million  pounds  of  surface  soil  about  7800  pounds  of  nitrogen,  2000 
pounds  of  phosphorus,  and  35,000  pounds  of  potassium. 


234  BULLETIN  No.  123.  [February, 

Iii  the  Middle  and  Upper  Illinoisan  glaciations,  which  are  older 
formations  and  have  the  natural  drainage  systems  better  developed, 
there  are  some  smaller  areas  of  black  clay  loam  but  in  those  areas 
this  type  of  soil  is  not  so  rich  in  plant  food.  In  the  Late  Wisconsin 
the  extent  of  this  type  is  quite  limited. 

Traces  of  acidity  are  sometimes  found  in  the  black  clay  loam, 
but  it  is  never  strongly  developed,  and  usually  the  subsoil  contains 
large  amounts  of  limestone.  (See  appendix  for  details.) 

The  first  problem  with  the  black  clay  loam  areas  has  always 
been  to  secure  adequate  drainage,  but  in  most  places  this  difficulty 
has  been  largely  overcome  by  making  large  open  dredge  ditches  and 
the  laying  of  drain  tile.  Most  of  this  land  has  been  brought  under 
profitable  cultivation  within  the  past  20  years  and  it  has  contributed 
much  toward  maintaining  the  average  crop  yields  of  the  corn  belt 
during  recent  years  when  the  yields  on  the  long-cultivated  lands 
have  been  decreasing. 

Where  properly  drained  this  black  clay  loam  will  continue  to 
produce  large  yields  for  many  years,  provided  sufficient  rotation  of 
crops  is  practiced  to  avoid  too  great  development  of  injurious  in- 
sects. It  is  probable  however  that  even  on  this  soil  the  best  results 
will  be  obtained  by  adopting  systems  of  farming  and  soil  treatment 
that  will  maintain  the  present  high  content  of  phosphorus  and  pre- 
vent too  great  depletion  of  humus  and  nitrogen. 

Investigations  should  be  started  at  once  to  secure  definite  infor- 
mation concerning  these  points.  As  yet  no  soil  experiment  fields 
have  been  established  on  black  clay  loam  because  of  the  much 
greater  present  need  for  experiments  on  soils  that  are  not  so  rich. 


This  type  of  soil  is  sometimes  called  red  clay  hill  land,  and  we 
have  in  a  previous  bulletin  (115)  called  it  red  silt  loam,  but  yellow 
better  describes  the  prevalent  color.  It  is  found  in  all  glaciations 
and  much  more  abundantly  (relatively)  in  the  unglaciated  areas. 
Like  most  of  the  soils  of  the  state,  it  consists  of  a  loessial  deposit. 
It  occupies  much  of  the  sloping  lands  or  hill  sides,  not  only  in  the 
original  hilly  sections  of  the  state  (the  unglaciated,  or  driftless, 
areas),  but  also  in  the  broken  land  regions  along  most  of  the  interior 
streams.  Under  ordinary  methods  of  cultivation  these  lands  are 
subject  to  serious  loss  from  surface  washing,  and  even  when  not 
under  cultivation  there  is  and  has  been  more  or  less  rapid  erosion 
taking  place.  Where  this  soil  has  been  under  ordinary  cultivation 
for  several  years  it  is  invariably  poor  in  humus  and  nitrogen  and 


/po<?.]  THE  FERTILITY  IN  ILLINOIS  SOILS.  235 

the  dominant  problem  is  to  maintain  or  increase  the  organic  matter 
in  the  soil,  which  will  also  increase  the  nitrogen,  which  is  a  constitu- 
ent part  of  ordinary  organic  matter. 

Of  course  the  organic  matter  must  in  large  part  at  least  be 
grown  upon  the  land  and  legume  crops  are  most  suitable  for  this 
purpose  because  their  growth  is  not  limited  by  the  small  nitrogen 
content  of  the  soil  and  they  also  furnish  green  manures  or  animal 
manures  rich  in  nitrogen. 

While  these  soils  are  not  rich  in  phosphorus,  that  element  does 
not  limit  the  yield  of  crops  because  the  nitrogen  limit  is  so  much 
lower  as  measured  by  crop  requirements  and  by  numerous  field  and 
pot  culture  experiments.  Furthermore,  by  surface  washing  the  ni- 
trogen, which  is  contained  only  in  the  humus,  is  rapidly  depleted 
while  the  phosphorus  is  constantly  renewed  because  of  the  supplies 
in  the  underlying  materials.  It  is  certain  that  for  the  highest  crop 
yields  phosphorus  must  be  applied,  and  very  probably  it  can  ulti- 
mately be  applied  with  profit  in  the  best  system  of  soil  improvement 
and  preservation,  but  as  stated  above  the  first  requisite  is  an  increase 
in  humus  and  nitrogen. 

There  is,  however,  a  serious  difficulty  to  the  growing  of  legume' 
crops,  especially  for  clover  and  alfalfa.  This  type  of  soil  where  it 
has  been  long  under  cultivation  is  markedly  sour  or  acid.  This 
applies  especially  to  the  unglaciated  yellow  silt  loam  (135)  in  the 
Ozark  Hills  region,  comprising  the  principal  type  of  upland  soil  in 
the  counties  of  Union,  Johnson,  Pope,  Hardin,  Alexander,  Pulaski, 
and  Massac;  and  also  to  the  Lower  Illinoisan  yellow  silt  loam 
(335)  which  occupies  much  of  the  sloping  hill  land  in  the  remain- 
ing counties  of  "Egypt,"  extending  northward  to  Shelby,  Cumber- 
land, and  Jasper. 

In  the  other  glaciations  this  type  of  soil  is  less  acid  than  in  the 
Lower  Illinoisan,  but  it  is  usually  more  or  less  acid  in  the  Middle 
and  Upper  Illinoisan,  in  the  Pre-Iowan  and  lowan,  and  even  in  the 
Early  Wisconsin  glaciation. 

The  acidity  is  evidently  at  least  very  largely  inorganic  in  char- 
acter. This  is  indicated  by  the  fact  that  the  organic  matter  de- 
creases rapidly  in  some  of  the  most  acid  soils  as  we  pass  from  sur- 
face to  subsoil  as  measured  either  by  total  nitrogen  or  by  total  or- 
ganic carbon,  whereas  in  strongly  acid  soils  the  acidity  increases 
with  depth  of  soil  and  is  several  times  stronger  in  the  subsoil  than 
in  the  surface.  Indeed,  in  many  strongly  acid  subsoils  the  acidity 
present  is  equivalent  to  several  times  the  total  possible  humic  acids 
basing  the  computations  upon  the  total  organic  carbon  and  upon 
the  accepted  formula  for  humic  acid  and  humates. 


236  BULLETIN   No.  123.  [February, 

Acid  silicates,  formed  from  polysilicates,  from  which  some  basic 
elements  may  have  been  removed  by  reaction  with  soluble  organic 
acids,  or  possibly  by  the  long-continued  weak  action  of  drainage 
waters  charged  with  carbonic  acid,  do  exist  in  the  soil  and  probably 
account  for  most  of  the  acidity  of  soils  that  are  at  the  same  time 
strongly  acid  and  very  deficient  in  humus. 

In  the  unglaciated  area  and  in  the  Lower  Illinoisan  glaciation 
initial  applications  of  at  least  two  tons  per  acre  of  ground  limestone 
are  recommended  for  the  yellow  silt  loam ;  and  for  the  other  glacia- 
tions  one  ton  or  more  may  well  be  applied  where  acidity  is  show^n 
in  the  surface  and  subsoil  and  where  difficulty  is  encountered  in  the 
growing  of  red  clover. 

One  cf  the  very  best  crops,  and  probably  the  most  satisfactory 
and  profitable  crop,  to  be  grown  on  these  yellow  silt  loam  soils  is 
alfalfa.  Its  power  to  secure  nitrogen  from  the  air,  to  root  deeply, 
and  to  live  for  many  years  are  all  very  great  advantages  for  this 
soil.  Furthermore,  experiments  have  shown  that  where  the  land 
is  properly  treated  with  heavy  applications  of  ground  limestone  and 
thoroughly  inoculated  with  the  alfalfa  bacteria  and  the  alfalfa 
seeded  on  well  prepared  and  well  manured  land  at  the  proper  time 
and  given  proper  care,  it  grows  luxuriantly  and  yields  large  and 
profitable  crops  on  this  soil.  On  the  other  hand  to  sow  20  to  25 
pounds  of  good  alfalfa  seed  on  this  soil  without  special  and  proper 
treatment  is  much  like  throwing  away  about  $4.00  an  acre. 

Of  course,  if  alfalfa  is  grown  on  this  land  it  should  all  be  fed 
on  the  farm  and  the  manure  returned  to  the  soil,  not  only  to  help 
the  alfalfa  but  also  for  other  crops  to  be  grown,  such  as  corn  and 
potatoes,  which  are  a  very  profitable  crop  for  this  soil  when  prop- 
erly enriched. 

Table  1 1  gives  the  yields  of  corn,  wheat,  and  clover  obtained  in 
1907  on  the  Vienna  soil  experiment  field  in  Johnson  county,  located 
on  the  less  rolling  phase  of  yellow  silt  loam  in  the  unglaciated  area. 

The  effect  of  the  ground  limestone,  applied  five  years  before, 
was  to  increase  the  crop  yields  in  1907  by  12.5  bushels  of  corn,  by 
6.9  bushels  of  wheatj  and  by  i.n  tons  of  clover  hay.  The  quality 
of  the  crops  was  also  improved,  especially  of  the  clover  which  was 
half  weeds  on  plots  I  and  2  without  limestone  but  good  clean  hay 
on  plots  3,  4,  and  5. 

At  35  cents  a  bushel  for  corn,  70  cents  for  wheat,  and  $6.00  a 
ton  for  air-dry  clover  hay,  the  value  of  the  increase  produced  by  the 
ground  limestone  amounts  to  $15.87  for  the  three  crops.  At  this 
rate  the  increase  would  pay  for  an  application  of  about  27  tons  of 


]  THE  FERTILITY  IN  ILLINOIS  SOILS.  237 

TABLE  11. — CROP  YIELDS  IN  SOIL  EXPERIMENTS:  VIENNA  FIELD 


Yellow  silt  loam  hill  land. 
Ung-laciated  area. 

Series  100 
corn, 
1907. 

Series  300 
wheat, 
1907. 

Series  200 
clover, 
1907. 

Value  of 
three  crops. 

Plot 

Soil  treatment  applied. 

Bushels  or  tons  per  acre. 

Total. 

In- 
crease. 

1 

2 

3 
4 

5 

None  

16.7 
17.8 
30.3 
37.1 

38.1 

4.3 
6.1 
13.0 
13.6 

15.6 

.65 
.81 
1.92 
2.56 

2.23 

$12.76 
15.36 
31.23 
37.87 

37.64 

$  2.60 
18.47 
25.11 

24.88 

Legume,  lime    

Legume,  lime,  phosphorus  . 

Legume,  lime,  phosphorus, 
potassium  

ground  limestone  per  acre  every  six  years,  which  is  three  times  the 
applications  actually  made  to  this  field,  the  effect  of  which  will 
last  many  more  years. 

Crop  yields  from  the  Vienna  soil  experiment  field  for  the  five 
previous  years,  1902  to  1906,  pot  culture  experiments  from  this 
type  of  soil  both  from  the  unglaciated  area  and  from  the  Upper 
Illinoisan  glaciation,  and  other  information  will  be  found  in  Bulle- 
tin 115,  "Improvement  for  the  Worn  Hill  Lands  of  Illinois,"  which 
together  with  Bulletin  76,  "Alfalfa  on  Illinois  Soil,"  and  Circular 
no,  "Ground  Limestone  for  Acid  Soils"  will  be  sent  free  of  charge 
upon  request  to  the  Agricultural  Experiment  Station,  Urbana,  Illi- 
nois. 

YELLOW  FINE  SANDY  LOAM  HILL  LAND  (864) 

This  type  of  soil  occupies  the  deep  loess  areas  covering  the 
bluffs  along  the  Mississippi  river,  the  lower  part  of  the  Illinois 
river,  and  to  a  less  extent  along  the  Ohio  and  Wabash  rivers.  It 
resembles  the  yellow  silt  loams  except  that  it  contains  more  very 
fine  sand  which  increases  usually  to  a  medium  sand  at  great  depth, 
in  consequence  of  which  the  soil  naturally  has  great  power  to  ab- 
sorb water  even  from  heavy  rainfall,  the  surplus  passing  into  the 
more  porous  lower  subsoil. 

Because  of  this  property  this  soil  does  not  suffer  from  surface 
washing  to  such  an  extent  as  would  be  expected  judged  only  from 
its  topography.  Of  course,  where  the  surface  soil  is  allowed  to 
become  very  deficient  in  organic  matter  its  power  of  rapidly  absorb- 
ing the  water  from  heavy  rainfalls  is  greatly  reduced  and  the 
tendency  to  "run  together"  is  greatly  increased,  both  of  which  lessen 
its  resistance  to  surface  washing. 


238  BULLETIN   No.  123.  [February, 

Frequently  pieces  of  light  shells  are  found  in  these  deep  loess 
deposits  indicating  river  loess,  and  Professor  Hosier  has  observed 
that  where  the  river  valley  is  wide  the  adjoining  strip  of  deep  loess 
over  the  bluffs  is  also  wide,  suggesting  a  distinct  relation.* 

Except  where  much  erosion  has  recently  occurred,  this  yellow 
fine  sandy  loam  is  acid  and  will  be  markedly  benefited,  especially  for 
clover,  alfalfa,  and  other  legumes,  by  liberal  applications  of  ground 
limestone.  At  least  one  or  two  tons  should  be  used  and  four  or  five 
tons  will  give  still  better  results,  especially  for  alfalfa,  for  the  grow- 
ing of  which  this  soil  when  properly  treated  is  probably  unexcelled. 

In  general  the  results  reported  above  and  in  Bulletin  115  re- 
garding the  yellow  silt  loams  apply  with  much  force  to  this  yellow 
fine  sandy  loam  of  very  similar  topography  and  chemical  composi- 
tion though  differing  in  some  physical  properties  in  favor  of  the 
deep  loess  soil. 

YEL,LOW-GRAY  SILT  LOAM 

The  yellow-gray  silt  loams  are  found  on  the  undulating  upland 
areas  that  are,  or  were  originally,  timbered.  The  topography  varies 
from  nearly  level  to  gently  rolling,  corresponding  to  the  topography 
of  the  brown  silt  loam  prairies. 

While  yellow -gray  silt  loam  is  found  to  some  extent  in  every 
glaciation  and  also  in  the  loess-covered  unglaciated  area,  it  is  as  a 
rule  much  less  extensive  than  the  prairie  lands  in  the  glaciated  areas 
and  much  less  extensive  than  the  yellow  silt  loam  in  the  more  roll- 
ing hill  land  regions,  as  in  the  unglaciated  area. 

In  the  Late  Wisconsin  glaciation,  which  consists  more  largely 
of  moraines  than  of  intermorainal  tracts,  the  yellow-gray  silt  loam 
(1034)  appears  t.o  be  relatively  more  extensive  than  in  any  other 
great  soil  area,  and  because  of  this  fact  this  soil  type  in  that  area 
is  included  in  this  report  of  the  general  soil  survey  of  the  state, 
while  in  other  areas  its  investigation  will  be  reported  only  in  con- 
nection with  the  detail  soil  survey  by  counties,  which  as  previously 
explained  is  already  well  under  way. 

The  yellow-gray  silt  loam  varies  from  yellow  to  gray  in  the 
surface  and  as  a  rule  there  is  more  or  less  "gray  layer"  in  the  sub- 
surface (especially  in  the  older  formations).  In  the  Late  Wiscon- 
sin glaciation,  the  loess  covering  being  shallow,  glacial  material 
containing  more"  or  less  gravel  is  frequently  found  in  the  subsoil 
within  40  inches  of  the  surface. 

*In  southern  Hardin  county  the  only  important  area  of  deep  loess  covers 
the  point  at  Rosiclare  which  is  exposed  to  a  long  sweep  of  wind  over  the  river 
bottoms  from  which  clouds  of  silt  and  sand  are  still  blown  by  strong  winds 
when  the  river  is  very  low  and  the  bottom  largely  uncovered. 


THE  FERTILITY  IN  ILLINOIS  SOILS.  239 

As  shown  in  Table  3,  the  Late  Wisconsin  yellow-gray  silt  loam 
(1034)  contains  in  the  surface  7  inches  about  2900  pounds  of  nitro- 
gen, 800  pounds  of  phosphorus,  and  47600  pounds  of  potassium. 
Compared  with  our  more  productive,  more  durable,  and  more  valu- 
able soils  (as  the  Early  Wisconsin  black  clay  loam),  this  soil  is 
very  poor  in  phosphorus  and  quite  low  in  humus  as  measured  by 
the  nitrogen  or  organic  carbon  (see  appendix),  while  it  is  extremely 
rich  in  potassium.* 

The  total  supply  of  phosphorus  in  the  plowed  soil  (7  inches 
deep)  is  less  than  would  be  required  for  35  crop's  of  corn  yielding 
100  bushels  of  grain  and  3  tons  of  stover,  while  the  total  nitrogen 
content  even  to  a  depth  of  40  inches  is  less  than  would  be  required 
for  60  such  crops,  or  for  less  than  90  crops  if  only  the  grain  were 
removed,  although  the  total  potassium  to  a  depth  of  40  inches  is 
sufficient  to  meet  the  requirements  of  a  zoo-bushel  crop  of  corn 
every  year  for  more  than  four  thousand  years,  or  for  more  than 
1 6  thousand  years  if  only  the  grain  is  removed.  Notwithstanding 
these  absolute  facts,  based  upon  accurate  chemical  analyses,  showing 
such  an  enormous  supply  of  potassium  and  a  relatively  small  supply 
of  nitrogen,  the  addition  of  soluble  potassium  salts,  while  not  yield- 
ing profitable  results,  has  actually  produced  a  larger  average  in- 
crease than  has  been  produced  by  nitrogen  applied  in  dried  blood 
on  the  Antioch  soil  experiment  field  in  Lake  county,  on  the  Late 
Wisconsin  yellow-gray  silt  loam,  thus  affording  a  good  illustration 
of  the  fact  that  systems  of  soil  treatment  for  permanent  agriculture 
should  not  be  based  solely  upon  previous  culture  experiments. 

*It  is  appropriate  to  mention  in  this  connection  that  Doctor  A.  S.  Cushman 
of  the  United  States  Department  of  Agriculture  has  recently  emphasized  (Sci- 
ence (1905)  22,  838;  and  U.  S.  Dept.  of  Agr.  Bureau  of  Plant  Industry  Bulle- 
tin 104)  the  possibility  of  using  powdered  granite  and  felspar  as  a  source  of 
potassium  for  fertilizing  purposes,  although  some  previous  experiments  with 
felspar  (Svenska  Mosskulturfor.  Tidskr.  (1903)  I7»  360;  (1904)  18.  33,  73) 
have  not  given  encouraging  results.  While  it  is  by  no  means  certain  that  gran- 
ite averaging  4  percent  of  potassium  or  felspar  with  8  or  10  percent  of  potas- 
sium may  not  be  used  with  profit  under  some  conditions,  as  where  it  can  be 
secured  as  waste  or  by-product  at  very  low  cost  near  lands  actually  deficient 
in  potassium,  it  is  worth  while  to  know  that  at  $3.00  per  ton  for  powdered  granite 
the  surface  soil  of  the  principal  types  in  the  Late  Wisconsin  glaciation  already 
contains  about  $1800  worth  of  potassium  per  acre  in  the  form  of  finely  pow- 
dered granitic  rock.  In  other  words,  two  tons  of  this  soil  (or  three  tons 
of  any  silt  loam  soil  in  the  Illinois  corn  belt)  spread  over  an  acre  of  land  would 
supply  as  much  potassium,  and  in  the  same  form,  as  would  be  supplied  by  a 
ton  of  average  powdered  granite. 

While  the  phosphorus  content  of  the  surface  soil  of  most  $150  Illinois  land 
can  be  doubled  by  investing  $25  to  $40  per  acre  in  raw  rock  phosphate  at  $8.00 
per  ton,  to  double  the  potassium  content  by  applying  powdered  granite  at  a 
cost  of  only  $3.00  a  ton  would  cost  from  $1200  to  $1800  per  acre. 


240 


BULLETIN  No.  123. 


[February, 


This  soil  is  deficient  in  active  humus  and  the  soluble  potassium 
salt  acts  in  large  part  at  least,  if  not  entirely,  as  a  soil  stimulant 
rather  than  as  plant  food.  As  already  shown  by  the  results  from 
Rothamsted,  England,  and  from  the  Fairfield  experiment  field, 
other  soluble  salts  may  produce  the  same  effect. 

In  Table  12  are  given  the  results  of  six  years'  work  on  the  Anti- 
och  soil  experiment  field. 

TABLE  12. — CROP  YIELDS  IN  SOIL  EXPERIMENTS — ANTIOCH  FIELD 


Soil 
plot 
Nos. 

Yellow-gray  silt  loam  undulat- 
ing timber  land:  L/ate  Wiscon- 
sin glaciation. 

Grain,  bushels  per  acre. 

Total 
Talue 
of  crops 
for  6 
years. 

1902 
corn. 

1903 
corn. 

1904 
oats. 

1905 
wheat. 

1906 
corn. 

1907 
corn. 

Treatment  applied. 

101 

102 

None         

44.8 
45.1 

36.6 
38.9 

17.8 
12.8 

18.5 
10.3 

35.9 
31.5 

12.4 
9.5 

$  62.80 
54.16 

103 
104 
105 

Lime,  nitrogen  

46.3 
50.1 

48.2 

40.8 
53.6 
50.2 

2.8 
12.5 
9.7 

17.8 
35.8 
21.7 

37.8 
57.4 
34.9 

6.4 
13.4 
12.9 

59.12 

89.27 
68.79 

Lime,  phosphorus  

Lime  potassium  

106 

107 

108 

Lime,  nitrogen, 
phosphorus.  

56.6 
52.1 

60  7 

62.7 
54.9 

66.0 

15.9 
10.3 

19.7 

15.2 
11.8 

28.7 

59.3 
39.0 

59.1 

20.9 
11.1 

18.3 

84.45 
65.83 

96.46 

Lime,nitrogen,  potassium 
Lime,  phosphorus, 

109 
110 

Lime,  nitrogen, 
phosphorus,  potassium. 
Nitrogen,  phosphorus, 

61.2 
59.7 

69.1 

71.8 

31.9 

37.2 

18.0 
16.3 

65.9 
66.3 

31.4 
28.8 

100.24 
100.02 

Ave 
Ave 
ph 
Ave 
po 

rage  gain  for  nitrogen  
rage  gain  for 

3.0 
9.2 
6.0 

4.7 
16.7 
11  0 

1.6 
11.1 
6.9 

-8.4 
9.0 

.3 

4.8 
24.6 

3.2 

3.9 
11.0 
5.9 

.26 
30.61 
11.08 

rage  gain  for 
tassium  

Plot  No.  i  is  naturally  better  land  than  the  others  and  both  i 
and  10  serve  only  as  checks  against  the  lime  treatment.  They  are 
not  used  in  studying  the  effects  of  plant  food  applied. 

The  oats  crop  in  1904  and  the  1907  corn  crop  were  almost  fail- 
ures. The  low  yields  of  wheat  from  plots  3,  6,  7,  and  9,  in  1905, 
were  due  to'  the  fact  that  the  wheat  on  these  nitrogen  plots  grew  very 
rank  and  Ipdged  badly  before  it  ripened.  The  straw  on  these  plots 
also  rusted  badly,  resulting  in  shriveled  and  light  grain. 

The  wheat  yields  on  plots  2,  4,  5,  and  8  are  more  trustworthy 
although  too  great  weight  must  never  be  placed  upon  the  results 
of  a  single  season. 


/pa?.]  THE  FERTILITY  IN  ILLINOIS  SOILS.  241 

The  total  gains  for  six  years  show  very  markedly  the  effects  of 
soil  treatment.  After  the  first  year  the  best  treated  plots  produced 
about  twice  as  much  as  plot  2  which  serves  properly  as  a  check  plot, 
to  which  no  nitrogen,  phosphorus,  or  potassium,  is  applied. 

Phosphorus  increased  the  total  value  of  the  six  crops  from 
$54.16  to  $89.26,  a  gain  of  $35.10  at  a  cost  of  $15  for  steamed 
bone  meal,  leaving  a  net  profit  of  $20.10  for  phosphorus,  or  $3.35 
per  acre  per  annum.  As  an  average  of  24  tests  under  different 
conditions  and  extending  over  six  different  seasons,  the  gross  in- 
crease produced  by  *6oo  pounds  of  nitrogen  applied  in  $90  worth 
of  dried  blood  amounts  to  26  cents,  or.  if  we  disregard  the  loss  on 
wheat,  it  amounts  to  $6.14. 

A  similar  average  shows  that  150  pounds  of  phosphorus  applied 
in  $15  worth  of  steamed  bone  meal  produced  an  increase  valued  at 
$30.61  with  a  net  profit  of  more  than  100  percent;  while  the  soil  is 
richer  in  phosphorus  than  six  years  ago  by  87  pounds  of  phosphorus 
per  acre. 

The  average  of  24  tests  shows  $11.08  gross  returns  from  $15 
invested  in  250  pounds  of  potassium.  Counting  that  50  pounds, 
or  $3.00  worth,  of  the  potassium  applied  still  remains  in  the  soil 
reduces  the  net  loss  to  about  $1.00. 

On  another  part  of  the  Antioch  soil  experiment  field  one  ton 
per  acre  of  raw  rock  phosphate  is  used  in  a  four-year  rotation  of 
corn,  corn,  oats,  and  clover,  started  in  1904.  Only  small  increases 
have  been  made  thus  far  on  the  grain  crops,  but  as  an  average  of 
four  different  tests  on  a  different  field  each  year  the  phosphate  in- 
creased the  yield  per  acre  of  air-dry  clover  hay  by  1.22  tons  in  1905 
and  by  .73  ton  in  1907.  Ultimately  increased  yields  of  clover  must 
result  in  larger  grain  crops  if  the  clover  hay  is  fed  and  proportionate 
amounts  of  manure  returned,  as  will  be  done  on  certain  plots. 

The  results  thus  far  secured  clearly  indicate  the  need  of  a  larger 
supply  of  total  phosphorus  and  of  more  active  humus  in  this  yellow- 
gray  silt  loam  of  the  undulating  timber  uplands. 

While  the  subsoil  in  the  Late  Wisconsin  glaciation  contains 
very  large  amounts  of  limestone  (see  appendix),  the  surface  soil 
is  sometimes  slightly  acid,  but  the  information  is  not  yet  sufficient 
to  determine  whether  the  addition  of  ground  limestone  is  advisable. 
It  may  be  stated  here  ho\vever  that  in  southern  Illinois,  especially 
in  the  Lower  Illinoisan  glaciation  and  in  the  unglaciated  area,  the 
yellow-gray  silt  loam  is  strongly  acid  and  should  receive  from  2 
to  5  tons  of  limestone  per  acre  as  an  initial  application,  especially 
for  the  more  successful  growing  of  clover. 


242  BULLETIN  No.  123.  [February, 

For  more  detailed  discussion  of  the  results  from  the  Antioch 
field,  Illinois  readers  are  referred  to  Circular  109,  "Improvement 
of  Upland  Timber  Soils  of  Illinois." 

IOWAN  BROWN  SANDY  LOAM  (760) 

This  type  of  soil  occupies  a  large  part  of  the  upland  in  the  lowan 
glaciation.  The  top  soil  consists  of  brown  sandy  loam  containing 
some  gravel  in  places  and  occasionally  pieces  of  stone.  The  subsoil 
at  a  depth  of  three  feet  or  more  frequently  contains  much  stone,  and 
the  proportion  of  stone  increases  with  the  depth,  the  disintegrating 
bed  rock  being  found  commonly  at  4  to  10  feet  beneath  the  surface. 

In  the  surface  and  subsurface  this  type  of  soil  is  usually  more 
or  less  acid,  but  the  pieces  of  stone  which  are  often,  though  not  al- 
ways, found  in  the  subsoil  above  40  inches  contain  some  limestone, 
the  underlying  bed  rock  being  on  impure  limestone. 

The  average  composition  of  the  lowan  brown  sandy  loam  shows 
3070  pounds  of  nitrogen,  850  pounds  of  phosphorus,  and  26,700 
pounds  of  potassium,  in  two  million  pounds  of  surface  soil.  While 
the  nitrogen  and  phosphorus  are  low  as  compared  with  rich  normal 
soils,  it  should  be  understood  that  porous  sandy  loam  soils  afford  a 
much  more  extensive  feeding  range  for  plant  roots  than  more  com- 
pact soils,  and  consequently  lower  percentages  of  plant  food  ele- 
ments may  be  adequate  for  the  production  of  large  crops  on  sandy 
loam  soils. 

On  the  other  hand  because  of  the  porosity  and  thorough  aera- 
tion of  sandy  soils  the  decomposition  of  organic  matter  is  rapid. 
Thus,  insoluble  organic  nitrogen  is  rapidly  converted  by  nitrification 
into  soluble  nitrates  and  with  the  perfect  natural  drainage  of  sandy 
loam  it  is  easily  carried  away  in  drainage  waters,  in  consequence 
of  which  nitrogen  is  much  more  likely  to  be  the  limiting  element  in 
sandy  soils  than  in  more  compact  silt  loams  or  clay  loams  of  equal 
nitrogen  content. 

The  Rockford  soil  experiment  field  is  located  on  the  lowan 
brown  sandy  loam,  about  three  miles  north  of  Rockford,  Winne- 
bago  county.  A  four-year  rotation  of  corn,  corn,  oats,  and  clover 
is  practiced  on  this  field  and  there  are  four  series  of  plots  so  that 
every  crop  may  be  represented  every  year,  including  first-year  corn, 
second-year  corn,  oats,  and  clover.  In  the  main  nitrogen  is  supplied 
by  legume  crops  and  farm  manure,  with  a  single  plot  in  each  series 
to  which  commercial  nitrogen  is  applied.  Phosphorus  is  applied  in 
raw  rock  phosphate  both  with  and  without  manure,  legume  catch 
crops,  and  potassium  sulfate,  singly  and  in  combination,  thus  mak- 


1908.]  THE  FERTILITY  IN  ILLINOIS  SOILS.  243 

ing  a  very  complete  and  practical  series  of  soil  experiments,  com- 
prising in  all  80  tenth-acre  plots. 

The  Rockford  field  has  been  in  operation  only  four  years  and 
the  different  systems  are  not  yet  fully  underway.  Thus  on  only 
one  series  and  for  only  one  year  has  first-year  corn  been  grown 
where  legume  catch  crops  have  been  previously  grown.  The  appli- 
cation of  manure  was  purposely  delayed  until  after  some  legume 
catch  crops  had  been  grown  and  plowed  under  in  order  to  afford  a 
comparison  between  these  two  methods  of  supplying  humus  and  ni- 
trogen. Of  course,  the  action  of  raw  rock  phosphate  will  be  slight 
at  best  in  the  absence  of  decaying  organic  matter.  Not  until  1909 
will  a  clover  crop  be  grown  on  manured  land,  and  1912  will  be  the 
first  year  in  which  oats  will  be  grown  on  land  manured  for  a  previ- 
ous clover  crop.  Thus,  land  manured  for  first-year  corn  in  1906 
should  be  in  clover  in  1909  and  the  corn  should  be  better  because 
of  the  previous  manuring.  Because  of  this  larger  yield  of  clover, 
and  of  consequent  larger  amounts  of  manure  to  be  returned,  larger 
yields  of  corn  should  follow  in  1910  and  1911  and  of  oats  in  1912. 

Some  interesting  and  valuable  results  are  to  be  looked  for  dur- 
ing the  next  four  years,  and  still  more  subsequently,  but  at  the 
present  time  the  average  results  are  to  be  considered  as  suggestive 
or  indicative  and  by  no  means  conclusive. 

As  an  average  of  four  years'  tests  140  pounds  of  nitrogen,  cost- 
ing $21.00  in  dried  blood,  have  increased  the  yield  of  corn  by  5.5 
bushels,  the  yield  of  oats  by  13  bushels,  and  (for  the  last  two  years 
only)  the  yield  of  clover  hay  by  .13  ton  per  acre. 

As  an  average  of  the  crops  grown  during  the  four  years,  appli- 
cations of  1000  pounds  to  i  ton  per  acre  of  rock  phosphate  increased 
the  yield  of  corn  by  2.6  bushels  per  acre  (32  tests),  the  yield  of  oats 
by  .9  bushel  (16  tests),  and  the  yield  of  clover  hay  by  .40  ton  (8 
tests  in  two  years). 

Potassium  applied  in  100  to  400  pounds  of  potassium  sulfate,  in 
addition  to  the  phosphorus,  produced  as  an  average  no  effect  on  the 
corn  or  oats,  and  only  .09  ton  increase  in  the  yield  of  clover  hay. 

These  results  indicate  that  nitrogen  is  the  limiting  element  in 
this  soil  and  that  phosphorus  also  produces  an  appreciable  effect, 
especially  on  clover.  Limestone  has  been  used  during  the  last  two 
years,  but  thus  far  without  benefit. 

As  an  average  of  six  tests  in  each  case  8  tons  of  manure  per 
acre  increased  the  yield  of  first-year  corn  by  5.6  bushels  in  1906 
ajid  of  second-year  corn  in  1907  by  5.7  bushels  on  the  same  plots 
without  further  manuring,  and  in  1907  on  another  series  of  plots 
8  tons  of  manure  increased  the  first-year  corn  by  9.1  bushels  per 
acre. 


244  BULLETIN  No.  123.  [February, 

Where  legume  catch  crops  (as  cowpeas  or  soybeans)  were 
seeded  in  the  corn  at  the  time  of  the  last  cultivation,  the  average 
effect  on  that  corn  crop  has  been  to  decrease  the  yield  about  2  bush- 
els, but  where  clover  ground  was  plowed  for  corn  in  1906  and 
legume  catch  crops  decreased  the  yield  of  corn  in  1906  by  1.3  bush- 
els, the  catch  crops  turned  under  for  the  next  year  increased  the 
second-year  corn  crop  in  1907  by  2.3  bushels  in  spite  of  the  catch 
crops  grown  in  the  corn  in  1907,  thus  suggesting,  but  not  yet  prov- 
ing, that  annual  legumes  as  catch  crops  in  the  corn  may  ultimately 
be  profitable. 

From  the  chemical  and  physical  composition  of  the  soil  and  from 
the  results  already  secured  from  the  field  experiments,  a  liberal  use 
of  farm  manure  and  of  legumes  in  rotation  crops  and  pastures  is 
recommended  for  this  soil.  Probably  the  use  of  rock  phosphate,  in 
addition  to  large  supplies  of  organic  matter,  will  prove  profitable 
but  further  data  are  necessary  to  settle  this  and  other  questions. 

BOTTOM  LAND  SOILS 

While  there  are  many  different  types  of  bottom  land  soil  in 
Illinois,  only  two  of  -the  most  important  and  extensive  types  have 
been  included  in  this  general  soil  survey  of  the  state. 

DEEP  GRAY  SILT  LOAM  (1331) 

Along  the  older  water  courses  affording  drainage  for  the  Illi- 
noisan  glaciation  (Lower,  Middle,  and  Upper)  and  for  the  ungla- 
ciated  area  the  principal  bottom  land  is  a  deep  gray  silt  loam  ( 133 1 ) . 
As  a  rule  this  land  is  still  subject  to  overflow  in  times  of  very  high 
water  and  the  soil  is  more  or  less  variable  in  its  content  of  humus, 
and  consequently  in  nitrogen  and  phosphorus  also.  Its  average 
composition  shows  about  3600  pounds  of  nitrogen,  1400  pounds  of 
phosphorus,  and  36,000  of  potassium  per  acre  in  the  surface  7 
inches.  Considering  that  the  subsoil  is  much  less  compact  than  in 
most  upland  silt  loams  and  affords  a  deeper  feeding  range  for  plant 
roots,  its  mineral  content  is  sufficient  for  large  crop  yields,  although 
long-continued  cropping  with  no  deposits  from  overflow  will  ulti- 
mately deplete  the  phosphorus  supply. 

The  soil  is  almost  invariably  more  or  less  acid  and  will  be  bene- 
fited, especially  for  the  growing  of  clover  or  alfalfa,  by  a  liberal  -use 
of  ground  limestone.  From  the  acidity  commonly  present  an  initial 
application  of  at  least  one  ton  of  limestone  per  acre  is  suggested,  and 
better  results  are  to  be  expected  from  applications  of  2  to  4  tons 
per  acre. 


iyo$.\  THE  FERTILITY  IN  ILLINOIS  SUILS.  245 

Aside  from  the  use  of  limestone  and  good  drainage  the  only 
immediate  recommendation  to  be  made  for  this  deep  gray  silt  loam 
is  to  maintain  a  sufficient  supply  of  decaying  organic  matter  by 
means  of  crop  i  otations  or  farm  manure. 

BROWN  LOAM  (1451) 

The  principal  soil  type  in  the  more  recent  bottom  lands,  as  in 
the  Wisconsin  glaciation  and  along  some  of  the  larger  streams,  in- 
cluding some  of  the  Mississippi  bottoms,  especially  north  of  the 
mouth  of  the  Kaskaskia  river,  is  a  brown  loam  (1451).  It  is  quite 
porous  and  friable  and  contains  more  sand  and  more  organic  mat- 
ter than  the  deep  gray  silt  loam  just  described.  As  a  rule  it  is  not 
markedly  acid  and  sometimes  contains  limestone,  although  slight 
acidity  is  liable  to  be  found  where  the  wash  has  been  partly  from 
the  older  Illinoisan  area. 

The  brown  loam  contains  in  the  surface  soil  about  4700  pounds 
of  nitrogen,  1600  of  phosphorus,  and  40,000  of  potassium,  being 
richer  in  every  constituent  than  the  deep  gray  silt  loam. 

Drainage,  protection  from  overflow  (or  better  control  of  over- 
flow), and  good  crop  rotation  should  produce  good  results  for  many 
years,  but  with  no  deposits  from  overflow  even  this  soil  will  ulti- 
mately become  deficient  in  phosphorus  if  the  crops  grown  are  re- 
moved, although  the  deep  feeding  range  afforded  will  postpone  the 
time. 

Other  bottom  land  soils,  of  which  there  are  many,  varying  from 
the  heaviest  plastic  clay  to  river  sand  and  gravel,  are  being  mapped 
and  investigated  in  connection  with  the  detail  soil  survey.  As  yet 
no  "soil  experiment  fields  have  been  established  on  bottom  land  soil, 
although  some  of  the  problems  relating  especially  to  heavy  plastic 
clay  soils  of  low  productive  power  covering  some  extensive  areas  of 
bottom  land  can  be  solved  only  by  field  experiments. 

SAND  AND  SWAMP  AREAS 

As  shown  on  the  general  survey  soil  map,  there  are  some 
extensive  areas  in  the  state  originally  covered  by  swamps,  sand 
plains  and  sand  ridges  or  dunes.  Notable  among  these  areas  are 
the  Inlet  Swamp  in  Lee  county,  the  Winnebago  and  Green  River 
Swamp  in  Lee,  Whiteside,  Bureau,  and  Henry  counties,  the  sand 
and  swamp  areas  in  Tazewell  and  Mason  counties,  and  the  Kanka- 
kee  Swamp  in  Kankakee  and  adjoining  counties. 

It  should  be  understood  that  boundaries  shown  on  the  general 
survey  soil  map  not  only  for  swamp  and  bottom  land  areas,  but  for 


246  BULLETIN   No.   123.  [February, 

moraines  and  great  soil  areas  are  not  located  with  exactness,  al- 
though in  the  main  they  are  very  approximately  correct.  So  far  as 
we  have  extended  the  detail  soil  survey  (the  mapping  of  twenty- 
seven  counties  being  nearly  completed  at  this  date),  we  have  found 
Leverett's  work  to  have  been  very  carefully  done.  Some  minor 
corrections  have  been  made  where  discovered  before  the  preparation 
of  the  accompanying  soil  map,  but  it  should  be  mentioned  here  that 
our  detail  work  shows  that  the  Vermilion  Swamp  or  wide  bottom 
land  shown  in  Ford  and  Livingston  counties  does  not  extend  to  the 
Illinois  river  in  LaSalle  county,  this  error  in  Leverett's  glacial  map 
having  been  found  too  late  to  be  corrected  in  our  soil  map. 

SAND  SOIL  (1481) 

Sand  soil  is  found  both  on  sand  plains  and  sand  dunes  where 
the  sand  has  been  blown  into  ridges  varying  from  narrow  drifts  to 
extensive  sand  hill  areas,  sometimes  covering  many  square  miles,  as 
in  Tazewell  and  Mason  counties. 

In  composition  this  soil  averages  about  1400  pounds  of  nitro- 
gen, 800  of  phosphorus,  and  31,000  pounds  of  potassium  in  the 
surface  7  inches  (2%  million  pounds).  The  high  percentage  of 
potassium  shows  that  this  soil  is  not  a  pure  quartz  sand,  but  is  to  a 
considerable  extent  of  granitic  origin. 

In  composition  this  soil  is  extremely  poor  in  nitrogen,  rich  in 
potassium,  and  fairly  well  supplied  with  phosphorus,  if  we  consider 
its  very  porous  character  and  the  very  deep  feeding  range  afforded 
to  plant  roots. 

The  Green  Valley  soil  experiment  field  is  located  on  sand  ridge 
soil  about  two  miles  southwest  of  Green  Valley,  Tazewell  county. 
The  soil  varies  from  a  very  sandy  loam  to  a  slightly  loamy  sand 
that  is  easily  drifted  by  the  wind  when  not  protected  by  vegetation. 
This  field  was  broken  out  of  pasture  in  1902.  In  Table  13  are  re- 
ported all  results  secured  in  six  years  from  that  part  of  the  Green 
Valley  field  where  nitrogen  as  well  as  other  elements  is  supplied  in 
commercial  form. 

Plots  i  (especially)  and  2  in  this  series  were  naturally  more 
productive  than  the  other  plots,  it  being  the  regular  custom  «.£  the. 
Experiment  Station  to  use  the  most  productive  land  tor  trie  un- 
treated check  plots  if  any  such  differences  are  apparent  when  the 
field  is  established,  as  was  the  case  in  this  instance.  Plot  I  serves 
only  as  a  check  against  the  lime  treatment,  and  the  average  of  plots 
2,  4,  5,  and  8  gives  a  more  reliable  basis  of  comparison  for  ascer- 
taining the  effect  of  nitrogen. 

A  four-year  rotation  of  corn,  corn,  oats,  and  wheat  is  practiced 
on  this  part  of  the  Green  Valley  field,  and  at  the  end  of  six  years 
we  are  at  the  middle  of  the  second  rotation. 


THE  FERTILITY  IN  ILLINOIS  SOILS. 
TABLE  13.  —  CROP  YIELDS  IN  Soil,  EXPERIMENTS:  —  GREEN  VALLEY 


247 


Soil 
plot 
Nos. 

Sand  ridge  soil. 

Grain,  bushels  per  acre. 

Total 
value 
of  crops 
for  6 
years. 

Treatment  applied. 

1902 
corn. 

1903 
corn. 

1904 
Oats. 

1905 
wheat. 

1906 
corn. 

1907 
corn. 

401 

402 

None  

68.7 
68.2 

56.3 
42.0 

49.7 
35.9 

18.3 
19.0 

32.9 
17.8 

35.3 
29.5 

$  92.86 
77.41 

Lime          

403 
404 
405 

Lime,  nitrogen  

68.6 
30.3 
23.1 

65.4 
24.9 
20.1 

44.4 
20.3 
16.9 

23.5 
16.7 
16.5 

62.9 
10.4 
8.4 

58.9 
13.1 
12.8 

117.08 

44.32 
38.32 

Lime,  phosphorus  

Lime,  potassium  

406 

407 
408 

Lime,  nitrogen, 
phosphorus  

57  4 
70.0 

49.8 

69.8 
72.9 

39.6 

51.9 
54.7 

36.9 

26.8 
36.5 

13.7 

70.8 
74.8 

18.3 

64.7 
73.6 

27.7 

123.69 
141.19 

66.21 

Lime,  nitrogen,  potassium 
Lime,  phosphorus, 
potassium  

409 
410 

Lime,  nitrogen, 
phosphorus,  potassium. 
Nitrogen,  phosphorus, 
potassium  

69.5 

57.2 

69.8 
66.1 

47.8 
50.0 

36.2 
26.5 

66.4 
66.0 

73.6 
71.9 

135.05 
122.47 

Aver 
Aver 

OV( 

Aver 
ph 

age  gain  for  nitrogen.  .  .  . 
age  gain  for  potassium 
;r  nitrogen  

23.5 
6.8 
-5.9 

37.8 
3.8 

.7 

22.3 
3.1 
.3 

14.3 
11.2 
1.5 

55.0 
3.8 
—  3 

46.9 
11.8 
2.9 

72.71 
17.79 

.22 

age  gain  for  phos- 
3rus  over  nitrogen  

To  facilitate  summarizing  the  six  years'  results  the  total  value  of 
the  six  crops  from  each  plot  is  shown  in  the  last  column,  and  at  the 
bottom  of  -the  table  are  shown  the  average  increase  in  yield  for  each 
year  and  the  total  value  of  the  six  years'  increase  ( i )  for  nitrogen 
under  the  four  conditions  (2)  for  phosphorus  in  addition  to  nitro- 
gen (2  tests  each  year),  and  (3)  for  potassium  in  addition  to  nitro- 
gen (2  tests  each  year).  Nitrogen  is  so  clearly  the  limiting  element 
that  the  only  question  regarding  phosphorus  and  potassium  is,  will 
either  of  them  effect  a  further  increase  after  nitrogen  has  been  ap- 
plied. 

As  an  average  of  four  tests  covering  six  years  the  addition  of 
nitrogen  to  this  sand  soil  has  produced  increases  valued  at  $72.71 
an  acre,  averaging  $12.12  a  year,  at  a  cost  of  $15.00  a  year  for 
100  pounds  of  nitrogen  in  dried  blood.  In  one  instance  the  increase 
produced  has  actually  exceeded  in  value  the  cost  of  the  nitrogen 
applied,  if  we  disregard  the  cost  and  effect  of  the  potassium.  Thus, 
the  total  value  of  the  six  crops  from  plot  5,  treated  with  lime  and 
potassium,  is  $38.32,  while  $141.19  is  the  corresponding  value  for 


248  BULLETIN   No.   123. 

plot  7,  which  differs  from  plot  5  only  by  the  addition  of  nitrogen. 
Under  these  conditions  600  pounds  of  nitrogen  costing  only  $90.00 
have  produced  an  increase  of  $102.87  per  acre  in  six  years. 

So  far  as  we  have  discovered  this  is  the  only  instance  where  the 
use  of  commercial  nitrogen  has  paid  its  cost  in  the  production  of 
ordinary  farm  crops  in  Illinois,  and  even  here  we  must  not  overlook 
the  fact  that  $15  worth  of  potassium  was  associated  with  the  $90.00 
worth  of  nitrogen  where,  this  enormous  increase  was  produced. 
While  potassium  without  nitrogen  produces  no  benefit  on  this  sand 
soil,  when  applied  with  nitrogen  the  potassium  has  produced  an 
average  increase  valued  at  $17.79  Per  acre  m  s^x  Years  at  a  cost  of 
$15.00,  but 'in  this  case  the  influence  and  cost  of  the  associated  nitro- 
gen must  not  be  ignored.  In  no  case  has  the  total  increase  paid  for 
the  combined  cost  of  the  elements  involved  with  nitrogen  as  one 
of  them. 

Potassium  is  evidently  the  second  limiting  element  in  this  soil 
where  decaying  organic  matter  is  not  provided,  but  the  limit  of 
potassium  is  very  far  above  the  nitrogen  limit. 

During  the  six  years  plot  7,  receiving  nitrogen  and  potassium, 
produced  291.3  bushels  of  corn  (averaging  72.5  bushels  a  year), 
54.7  bushels  of  oats,  and  36.5  bushels  of  wheat,  per  acre.  To  pro- 
duce the  increase  of  plot  7  over  plot  5  would  require  about  75  per- 
cent of  the  total  nitrogen  applied.  Thus,  there  has  been  a  loss  of 
25  percent  of  the  nitrogen  applied,  which  is  a  smaller  loss  than  usu- 
ally occurs  where  commercial  nitrogen  is  used.  Without  doubt 
larger  yields  would  have  been  produced,  especially  of  corn,  if  150 
or  200  pounds  of  nitrogen  per  acre  per  annum  had  been  used,  which 
would  have  increased  the  cost  of  nitrogen  to  $22.50  or  $30.00,  re- 
spectively, per  acre  each  year. 

It  need  scarcely  be  mentioned  that  commercial  nitrogen  is  used 
in  these  and  other  experiments  in  Illinois  only  to  help  discover  what 
elements  are  limiting  the  crop  yields.  It  should  never  be  purchased 
for  use  in  general  farming,  but,  if  needed,  secured  from  the  atmos- 
phere by  legume  crops  to  be  returned  to  the  soil  directly  or  in 
manure. 

It  is  interesting  to  note  that  on  the  sand  soil  the  six  years'  in- 
crease from  $15.00  worth  of  phosphorus  (even  when  applied  with 
nitrogen)  is  valued  at  only  22  cents,  while  on  the  yellow-silt  loam 
soil  on  the  Antioch  field  (Table  12)  26  cents  represents  the  total 
increase  from  the  use  of  $90.00  worth  of  nitrogen.  Thus  do  soils 
differ.  (See  also  peaty  swamp  land  results  described  below). 

On  three  other  series  of  plots  on  the  Green  Valley  soil  experi- 
ment field  a  three-year  rotation  of  corn,  oats,  and  cowpeas  is  prac- 


1908.]  THE  FERTILITY  IN  ILLINOIS  SOILS.  249 

ticed,  every  crop  being  represented  every  year.  On  plots  receiving 
lime  and  phosphorus  and  legume  crops,  as  green  manure,  the  yield 
of  corn  was  45.6  bushels  in  1906  and  67.8  bushels  in  1907,  com- 
pared with  70.8  bushels  and  64.7  bushels  with  lime,  phosphorus,  and 
nitrogen  on  plot  6  (see  Table  13)  and  with  10.4  bushels  and  13.1 
bushels  with  no  nitrogen  on  plot  4,  for  the  respective  years.  On 
other  plots  receiving  comparable  treatment,  where  lime,  phosphorus, 
and  potassium  were  used  with  nitrogen-gathering  legume  crops  as 
green  manure  the  corn  yields  in  the  three-year  rotation  were  54.6 
bushels  in  1906  and  51.5  bushels  in  1907,  compared  with  66.4  bush- 
els and  73.6  bushels  on  plot  9  with  nitrogen  applied,  and  compared 
with  18.3  bushels  and  27.7  bushels  on  plot  8  with  no  nitrogen  for 
the  same  years. 

The  growing  of  legume  crops  and  the  use  of  farm  manure  (and 
possibly  limestone)  are  the  only  recommendations  made  for  the 
improvement  of  these  well  drained  sand  soils,  although  further 
tests  may  show  profit  from  potassium  until  more  organic  matter  is 
supplied.  As  a  rule  clover  cannot  be  grown  successfully  on  this 
land,  but  cowpeas  and  soybeans  are  well  adapted  to  such  soil  and 
they  produce  very  large  yields  of  excellent  hay  or  of  grain  very 
valuable  for  feed  and  also  for  seed. 

Under  the  best  conditions  with  good  preparation  and  heavy 
manuring  alfalfa  can  be  grown  on  this  sand  soil,  more  than  five 
tons  of  alfalfa  hay  per  acre  in  one  year  having  been  grown  on  part 
of  the  Green  Valley  field.  Both  soybeans  and  alfalfa  should  be  in- 
oculated with  the  proper  nitrogen-fixing  bacteria.  (See  Plate  7.) 

Heavy  applications  of  ground  limestone  also  may  be  especially 
beneficial  in  getting  alfalfa  started. 

For  more  detailed  information  the  reader  is  referred  to  Bulletin 
76,  "Alfalfa  on  Illinois  Soil,"  and  Bulletin  94,  "Nitrogen  Bacteria 
and  Legumes." 


250 


BULLETIN  No.  123. 


[February, 


« 


I?  <J 

M    fH 

^g 
M     O 

w  o 
w^ 

r- 

<!  << 

«pq 


/po<?.]  THE  FERTILITY  IN  ILLINOIS  SOILS.  251 

x  PEATY  SWAMP  LANDS 

Peat  is  chiefly  of  two  kinds,  one  being  known  as  moss  peat  and 
the  other  as  grass  peat.  Moss  peat  consists  largely  of  dead  and 
decaying  sphagnum  moss,  and  grass  peat  of  the  residues  of  coarse 
swamp  grass,  sedge,  flags,  etc. 

Probably  most  of  the  Illinois  beds  are  grass  peat,  although  there 
is  some  moss  peat  in  the  state.  Indeed,  in  the  detail  soil  survey  of 
Lake  county  one  swamp  of  several  acres  was  found  where  the 
sphagnum  moss  is  still  growing  luxuriantly  over  a  bed  of  moss  peat. 

Where  the  soil  consists  very  largely  of  decaying  peat  to  a  depth 
of  30  inches  or  more,  it  is  called  deep  peat  (Soil  Type  No.  1401). 

As  shown  in  Table  3,  deep  peat  contains  in  one  million  pounds 
of  surface  soil  about  35,000  pounds  of  nitrogen,  2000  pounds  of 
phosphorus,  and  2900  pounds  of  potassium.  This  shows  in  the  sur- 
face 7  inches  of  an  acre  about  five  times  as  much  nitrogen  as  the 
Early  Wisconsin  black  clay  loam  prairie.  In  phosphorus  content 
these  two  soil  types  are  about  equal,  but  the  peat  contains  less  than 
one-tenth  as  much  potassium  as  the  black  clay  loam.  Thus  the  total 
supply  of  potassium  in  the  peat  to  a  depth  of  7  inches  (2930 
pounds)  would  be  equivalent  to  the  potassium  requirement  (71 
pounds)  of  a  hundred-bushel  crop  of  corn  for  only  41  years,  or  if 
the  equivalent  of  only  one-fourth  of  one  percent  of  this  is  annually 
available  in  accordance  with  the  rough  estimate  previously  sug- 
gested, about  7  pounds  of  potassium  would  be  liberated  annually,  or 
sufficient  for  about  10  bushels  of  corn  per  acre. 

In  Table  14  are  given  all  results  obtained  from  the  Manito  ex- 
periment field  on  deep  peat,  which  was  begun  in  1902  and  discon- 
tinued after  1905.  The  plots  in  this  field  were  one  acre*  each  in 
size,  being  two  rods  wide  and  80  rods  long,  and  untreated  half-rod 
division  strips  were  left  between  the  plots,  which,  however,  were 
cropped  the  same  as  the  plots. 

The  results  of  four  years'  tests  as  given  in  Table  14  are  in  com- 
plete harmony  with  the  information  furnished  by  the  chemical  com- 
position of  peat  soil  as  compared  with  that  of  ordinary  normal  soils. 
Where  potassium  was  applied  the  yield  was  from  three  to  four 
times  as  large  as  where  nothing  was  applied.  Where  approximately 
equal  money  values  of  kainit  and  potassium  chlorid  were  applied 
slightly  greater  yields  were  obtained  with  the  potassium  chlorid, 
which,  however,  supplied  about  one-third  more  potassium  than  the 
kainit.  On  the  other  hand,  either  material  furnished  more  potas- 
sium than  was  required  by  the  crops  produced. 

*In  1904  the  yields  were  taken  from  quarter-acre  plots  because  of  severe 
insect  injury  on  the  other  part  of  the  field. 


252 


BULLETIN  No.  123. 


[February, 


TABLE  14. — CORN  YIELDS  IN  Son,  EXPERIMENTS:     MANITO  FIELD 
TYPICAL  DEEP  PEAT  Son, 


Plot. 
No. 

Soil  treatment 
for  1902. 

Corn 
1902, 
bu. 

Corn 
1903, 
bu. 

Soil  treatment 
for  1904. 

Corn 
1904 
bu. 

Corn 

1905 
bu. 

Four 
crops, 
bu. 

1 

2 

3 

4 

5 
6 

7 

8 
9 
10 

None  

10.9 
10.4 

30.4 

30.3 

31.2 
11.1 

13.3 

36.8 
26.4 
14.9* 

8.1 
10.4 

32.4 

33.3 

33.9 
13.1 

14.5 

37.7 
25  1 
14.9 

None   

17  0 
12.0 

49.6 

53.5 
48.5 
24.0 

44.5 
44.0 
41.5 
26.0 

12.0 
10.1 

47.3 

47.6 

52.7 
22.1 

47.3 
46.0 
32.9 
13.6 

48.0 
42.9 

159.7 

164.7 
166.3 
70.3 

164.5 
125.9 
69.4 

None  

Limestone,  4000  Ib. 

I  Limestone,          ) 
4000  Ib.  [• 
(  Kainit,  1200  Ib.  ) 

(  Kainit,  1200  Ib.  ) 
•\  Steamed  bone,    > 
(                    395  Ib   ) 

{  Potassium           | 
\  chlorid,  400  Ib.    f 

None  

Kainit,  600  Ib  

I  Kainit,  600  Ib.     J 
\  Acidulated 
(        bone,  350  Ib.  ) 

j  Potassium           } 
|  chlorid,  200  Ib.    j 

j  Sodium                 ) 
(  chlorid,  700  Ib.    \ 

(  Sodium                 ) 
1  chlorid,  700  Ib.    f 

Kainit,  600  Ib  

Kainit,  1200  Ib  

Kainit,  600  Ib  

Kainit,  300  Ib  

Kainit,  300  Ib  

None  

None  :  

^Estimated  from  1903;  no  yield  was  taken  in  1902  because  of  misunder- 
standing'. 

The  use  of  700  pounds  of  sodium  chlorid  (common  salt)  pro- 
duced no  appreciable  increase  over  the  best  untreated  plots,  indicat- 
ing that  where  potassium  is  itself  actually  deficient,  salts  of  other 
elements  cannot  take  its  place. 

Applications  of  two  tons  per  acre  of  ground  limestone  produced 
no  increase  in  the  corn  crops,  neither  when  applied  alone  nor  in 
combination  with  kainit,  neither  the  first  year  nor  the  second. 

Reducing  the  application  of  kainit  from  600  to  300  pounds,  for 
each  two-year  period,  reduced  the  yield  of  corn  from. 164.5  to  I25-9 
bushels.  The  two  applications  of  300  pounds  of  kainit  furnished 
60  pounds  of  potassium  for  the  four  years,  or  sufficient  for  84  bush- 
els of  corn  (grain  and  stalks).  The  difference  between  this  and 
the  125.9  bushels  obtained  is  42  bushels,  about  what  was  obtained 
from  the  poorest  untreated  plot. 

The  underdrainage  provided  for  this  experiment  field  was  not 
sufficient  for  the  best  results,  probably  because  of  insufficient  nitri- 
fication. In  other  experiments  on  peaty  soil  with  imperfect  drain- 
age the  addition  of  $15  worth  of  nitrogen  with  potassium  produced 
.about  15  bushels  more  corn  than  where  potassium  alone  was  used. 


iyoS.]  THE  FERTILITY  IN  ILUNOIS  SOILS.  253 

OTHER  PEATY  AND  ALKALI  SOILS    , 

Aside  from  deep  peat,  there  are  many  other  types  of  peaty  soil, 
as  will  be  seen  from  the  classification  of  Illinois  soil  types  given  in 
the  appendix.  Thus  we  find  shallow  peat  and  medium  peat,  under- 
lain with  clay,  sand,  rock,  etc.,  and  also  sandy  peat  and  peaty  loam; 
and  in  some  instances  peaty  soils  also  contain  alkali,  consisting 
chiefly  of  harmless  calcium  carbonate  (limestone)  with  smaller 
amounts  of  injurious  magnesium  carbonate. 

In  some  cases  these  peaty  soils  actually  contain  a  good  percent- 
age of  total  potassium,  more  commonly  in  the  subsurface  or  subsoil, 
but  sometimes  in  the  surface  soil  also,  and  yet  the  untreated  soil  is 
unproductive  while  the  addition  of  potassium  salts  produces  large 
and  very  profitable  increases  in  the  yield  of  corn,  oats,  etc. 

In  pot  culture  experiments  we  have  even  been  able  by  the  addi- 
tion of  potassium  sulfate  to  correct  to  a  considerable  extent  the  in- 
jurious property  of  magnesium  carbonate  that  has  been  purposely 
applied  to  ordinary  brown  silt  loam  prairie  soil  which  is  known  to 
contain  abundance  of  available  potassium. 

These  facts  are  mentioned  here  because  we  recommend,  tenta- 
tively, the  application  of  potassium  salt  to  all  classes  of  peaty  and 
alkali  soils  that  are  unproductive  after  being  well  drained,  when- 
ever the  supply  of  farm  manure  is  insufficient.  It  should  be  under- 
stood that  plenty  of  farm  manure,  preferably  quick-acting,  or  read- 
ily decomposable,  manure,  such  as  horse  manure,  will  supply  potas- 
sium and  thus  accomplish  everything  that  potassium  salts  can  ac- 
complish, and  on  some  swamp  soils  manure  produces  good  results 
where  potassium  is  without  effect. 

In  pot  culture  experiments  soils  containing  injurious  amounts 
of  magnesium  carbonate  have  been  treated  with  calcium  sttlfats 
(landplaster)  which  brings  about  a  double  decomposition,  or  intet- 
change,  forming  the  harmless  insoluble  calcium  carbonate  (lime- 
stone) and  the  very  soluble  magnesium  sulfate,  which  is  subse- 
quently leached  out,  leaving  the  soil  productive. 

The  new  Manito  experiment  field,  located  three  miles  east  of 
Manito  in  Tazewell  county  on  the  Mason  county  line,  is  on  alkali 
soil  consisting  of  peaty,  clayey  sand  with  some  gravel,  and  contain- 
ing sufficient  total  potassium  for  normal  crop  yields. 

In  Table  15  are  recorded  the  treatment  applied  and  results  ob- 
tained in  1907  on  the  new  Manito  field. 


254 


BULLETIN   No.  123. 


[February, 


TABLE  15. — CORN  YIELDS  IN  SOIL  EXPERIMENTS:— NEW  MANITO  FIELD, 
PEATY  ALKALI  SOIL 


Plot  No. 

Treatment  applied  for  1907. 

Corn  , 
bu.  per  acre. 

201 

None  

8.8 

202  W 

Manure,  6  tons  

43.5 

202  E 

Manure,  12  tons  

64.9 

203 

Potassium  sulf  ate,  400  pounds  

73.0 

204 

Calcium  sulfate,  2  to  16  tons  

4.9 

205 

None  

5.4 

Plot  204  is  divided  into  four  equal  parts  and  the  calcium  sulfate 
applied  at  the  rate  of  2  tons,  4  tons,  8  tons,  and  16  tons,  per  acre, 
at  a  cost  of  $6.00  per  ton.  It  produced  no  benefit  in  1907.  Whether 
it  will  assist  in  the  removal  of  the  magnesium  carbonate  by  double 
decomposition  and  leaching  and  thus  improve  the  soil  in  time,  time 
alone  will  tell. 

The  400  pounds  of  potassium  sulfate  are  applied  for  a  three-year 
rotation  at  an  initial  cost  of  $10.00.  The  increase  of  66  bushels  of 
corn  produced  the  first  year,  at  35  cents  a  bushel,  amounts  to  more 
than  twice  the  total  cost  of  the  potassium.  The  manure  also  gave 
very  excellent  results. 

In  Table  16  are  given  all  results  obtained  during  six  years'  ex- 
periments on  part  of  the  Momence  soil  experiment  field,  located 
three  miles  south  of  Momence,  Kankakee  county,  on  peaty  swamp 
land  which  contains  much  decaying  peat  and  coarse  sand  in 
the  surface  and  in  the  subsurface,  with  a  clayey  sand  subsoil  resting 
on  impure  limestone,  while  the  surface,  subsurface,  and  subsoil  con- 
tain more  than  half  of  the  normal  amounts  of  total  potassium  (19,- 
ooo,  47,000,  and  73,000  pounds,  respectively,  per  acre).  The  soil 
contains  but  little  alkali. 

After  1902  (when  the  corn  was  damaged  by  water)  the  land 
was  tile-drained  sufficiently  well  for  ordinary  years,  but  in  the  ex- 
tremely wet  season  of  1907  the  corn  was  planted  very  late  and  with 
the  continued  wet  weather  resulted  in  almost  a  complete  failure. 

Potassium  was  not  applied  to  plot  102  for  1902  and  1903  and 
was  not  applied  to  plot  no  for  1904. 

The  untreated  check  plot  101  is  naturally  somewhat  more  pro- 
ductive than  the  other  plots. 


/po<?.]  THE  FERTILITY  IN  ILLINOIS  SOILS. 

TABLE  16.— CROP  YIELDS  IN  SOIL  EXPERIMENTS:  MOMENCE  FIEI,D 


Plot 
No. 

Peaty  swamp  land. 

Corn 

1902. 

Corn 
1903. 

Corn 
1904. 

Corn 
1905. 

Corn 
1906. 

Corn 
1907. 

6  Crops. 

Soil  treatment  applied. 

Bu. 

Value. 

101 

102 

None         

6.9 

5.5 

14.9 
7.1 

4.8 
20.1' 

6.8 
33.9 

6.8 
52.6 

.3 
14.9 

40.5 

$14.18 
* 

Lime  (and  potassium 
after  2  years)  

103 
104 

105 

Ivime,  nitrogen  

0.0 
1.3 

23.7 

3.6 
4.6 

72.2 

1.3 
.4 
34.6 

4.1 
1.8 
41.4 

5.3 
1.9 
50.0 

.4 
.2 
16.2 

14.7 
10.2 
238.1 

5.15 
3.57 
83.34 

L/ime,  phosphorus  

lyim  c,  potassium     

106 

107 

108 

L/ime,  nitrogen, 
phosphorus  

0.0 
19.7 

32.0 

3.9 
71.1 

73.1 

.6 

33.5 

42.0 

1.6 

38.5 

36.3 

4.5 
53.1 

59.4 

.4 
16.5 

19.9 

11.0 

232.4 

262.7 

3.85 
81.34 

91.95 

Ivime,  nitrogen,  potassium 
Ivime,  phosphorus, 
potassium  

109 
110 

Lime,  nitrogen, 
phosphorus,  potassium.  . 
Nitrogen,  phosphorus, 
potassium 

25.2 
24.1 

66.8 
70.4 

39.2 
19.0 

42.9 
24.8 

65.6 

51.3 

25.1 
23.4 

264.8 

92.68 

*In  the  table  on  the  last  page  the  average  value  from  plots  103,  104,  and  106  is 
shown  but  not  used  for  computing  increase. 

These  results  from  the  new  Manito  field  and  from  the  Momence 
field,  on  abnormal  swamp  lands,  as  well  as  the  results  from  DuBois 
and  Antioch,  emphasize  the  fact  that,  although  some  principles  are  • 
well  established  and  can  be  applied  with  normal  results  on  normal 
soils,  there  are  complex  problems*  still  unsolved  relating  to  some 
soils  of  large  extent  and  of  vast  importance  to  the  state. 

Further  information  concerning  this  group  of  soils  is  given  in 
Bulletin  No.  93,  "Soil  Treatment  for  Peaty  Swamp  Land,  including 
Reference  to  Sand  and  Alkali  Soil,"  but  unfortunately  the  supply  of 
this  bulletin  is  completely  exhausted.  A  second  edition,  including 
additional  information  will  be  published  as  soon  as  possible. 

*These  problems  may  be  chemical,  physical,  or  biological,  and  their  solution 
may  require  the  application  of  science  yet  unknown.  Thus,  some  essential  ele- 
ment of  plant  food  may  be  present  in  abundance  but  held  in  unavailable  form  by 
chemical  combination  or  physical  absorption;  or  there  may  exist  in  the  soil 
still  undiscovered  some  chemical  substance  injurious  to  agricultural  plants  or 
to  necessary  bacterial  life;  and  the  recent  very  extensive  investigations  by  the 
United  States  Bureau  of  Soils  indicate  that  conditions  may  be  brought  about, 
artificially  at  least,  in  which  organic  toxic  substances  develop  that  are  injurious 
to  plant  growth. 


256 


BULLETIN  No.  123. 


[February, 


S  pq 


fa  O 

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gg 

fa  M 


THE  FERTILITY  IN  ILLINOIS  SOILS. 


APPENDIX  A. 
CLASSIFICATION  OF  ILLINOIS  SOILS 

In  the  systematic  or  detail  soil  survey  of  the  state  the  soils  of 
Illinois  are  classified  first  according  to  the  14  great  soil  areas  based 
upon  the  age  or  general  method  of  formation. 

GREAT  SOIL  AREAS  OF 


Number  in  hundreds. 


100 

200 

300 
400 
500 

600 
700 

800 

900 

1000 
1100 
1200 

1300 
1400 


Name. 


Unglaciated  areas 

Illinoisan  moraines   

Lower  Illinoisan  glaciation. 
Middle  Illinoisan  glaciation 
Upper  Illinoisan  glaciation 

Pre-Iowan  glaciation 

lowan  glaciation 

Deep  loess  areas . 

Early  Wisconsin  moraines. . 
I/ate  Wisconsin  moraines. .  . 
Early  Wisconsin  glaciation 
L,ate  Wisconsin  glaciation.  . 


Old  river  bottom  and  swamp  areas.  . 
Sand,  late  swamp  and  bottom  lands 


Within  these  great  soil  areas  the  soils  are  classified  in  the  fol- 
lowing general  groups,  and  within  the  limits  of  the  numbers  given : 


SOILS  :     GENERAL  GROUPS 


Number 
Limits 

Group  Names 

Number 
Limits 

Group  Names 

o  to    9.  .  . 

.  .  Peats 

en   to    $Q 

Loams 

10  to  12.  .  . 

.  .  Peaty  loams 

60  to  79 

Sandy  loams 

13  to  14.  ..  . 

.  .  Mucks 

80  to  89  

.  .  Sands 

15  to  19.  . 

.  .  Clays 

no  to  QJ. 

20   to   24.  .. 

.  .  Clay  loams 

ne   to  07 

Gravels 

25  to  49.  .  . 

.  .Silt   loams 

98.. 

.  .  Stony  loams 

99  

.  .Rock  outcrop 

In  the  final  system  of  numbering  and  classifying  individual  soil 
types  the  Dewey  library  system  of  numbers  is  used,  whole  numbers 
being  assigned  .to  important  and  definite  soil  types  and  decimals 
employed  for  related  types  possessing  some  distinct  variations.  In 
all  cases  the  name  is  designed  to  carry  with  it  as  complete  a  descrip- 
tion as  practicable  of  the  soil  type,  so  as  to  avoid  any  unnecessary 
tax  on  the  memory  of  the  student  or  farmer.  Following  is  a  list 
of  the  soil  types  thus  far  recognized  in  the  detail  soil  survey  of 


258 


BULLETIN   No.   123. 


[February, 


Illinois.  It  should  be  understood,  however,  that  to  designate  the 
individual  soil  type  requires  the  soil  area  name  and  number  (as 
hundreds)  to  be  prefixed  to  the  following  soil  type  names  and  num- 
bers. Thus,  the  Middle  Illinoisan  brown  silt  loam  (426)  is  not  the 
same  soil  type  as  the  Late  Wisconsin  brown  silt  loam  (1026),  as 
will  be  seen  from  the  preceding  pages.  Also  the  Old  Bottom  Land 
deep  gray  silt  loam  (1331)  is  not  the  same  individual  type  as  the 
Lower  Illinoisan  deep  gray  silt  loam  (331),  a  type  found  in  small 
areas  on  the  upland  prairies  in  that  glaciation,  but  not  discussed  in 
this  bulletin.  (The  word  "on"  is  used  for  depths  less  than  40  inches, 
while  "over"  is  used  for  greater  depths.) 

ILLINOIS  SOIL  TYPES 


No. 


Name 


No. 


Name 


I 

2.  ... 

2.1.  . 

2.2.  . 
2.3-. 
3-... 

3.1. • 

3-2.. 

3-3-. 
10 

IO.I.. 
IO.2. . 
10.3.. 
13--.. 
I3.I.. 
13-2.. 
I3-3-. 
IS-.-- 
I5-I-. 
15-2,. 

16.... 

20 

20. i. . 

2O. 2. . 

21 

21 

22 

25 

25 

26.... 

26.1.. 

26.2. . 

26.3.. 

26.4.  . 

26.5.. 

27.... 

28.... 

29.     .. 

29.1. . 

30.,.. 


,1. 


I. 


.  .Deep  peat 

. .  Medium  peat  on  clay 

. .  Medium  peat  on  clayey  sand 

.  .Medium  peat  on  sand 

. .  Medium  peat  on  rock 

.  .Shallow  peat  on  clay 

..Shallow  peat  on  clayey  sand 

..Shallow  peat  on  sand 

. .  Shallow  peat  on  rock 

. .  Peaty  loam  on  clay 

. .  Peaty  loam  on  clayey  sand 

. .  Peaty  loam  on  sand 

. .  Peaty  loam  on  rock 

. .  Muck  on  clay 

. .  Muck  on  clayey  sand     . 

.  .Muck  on  sand 

.  .Muck  on  rock 

.  .Drab  clay 

.  .Sandy  drab  clay 

.  .Gravelly  drab  clay 

.  .Gray  clay 

. .  Black  clay  loam 

.  .Sandy  black  clay  loam 

..Gravelly  black  clay  loam 

.  .Drab  clay  loam 

.  .Drab  clay  loam  on  sand 

. .  Gray  clay  loam 

.  .Black  silt  loam 

.  .Black  silt  loam  on  clay 

.  .Brown  silt  loam 

.  .Brown  silt  loam  on  clay 

.  .Brown  silt  loam  on  sand 

.  .Brown  silt  loam  on  till 

.  .Brown  silt  loam  on  gravel 

. .  Brown  silt  loam  on  rock 

.  .Brown  silt  loam  over  gravel 

.  .Brown-gray  silt  loam  on  tight  clay 

.  .Drab  silt  loam 

.  .Drab  silt  loam  on  clay 

.  .Gray  silt  loam  on  tight  clay 

.  .Deep  gray  silt  loam 


32 Light  gray  silt  loam  on  tight  clay 

32.1 White  silt  loam  on  tight  clay 

33 Gray-red  silt  loam  on  tight  clay 

34 Yellow-gray  silt  loam 

34. 1 Yellow-gray  silt  loam  on  tight  clay 

35 Yellow  silt  loam 

35.1. ..  .Yellow  silt  loam  on  tight  clay 

35.2 Yellow  silt  loam  on  clay 

35-3. ..  .Yellow  silt  loam  on  sand 
35.4. ..  .Yellow  silt  loam  on  gravel 

35-5 Yellow  silt  loam  on  rock 

50 Black  loam 

50. 1. ..  .Black  loam  on  clay 

5r. Brown  loam 

51.1. ..  .Brown  loam  on  clay 
51.2. ..  .Brown  loam  on  silt 
51.3. ..  .Brown  loam  on  sand 
51.4. ..  .Brown  loam  on  gravel 
51.5. ..  .Brown  loam  on  rock 

52 Gray  loam 

S3 Yellow  loam 

54 Mixed  loam 

60 Brown  sandy  loam 

60. 1. ..  .Brown  sandy  loam  on  silt 

60.2 Brown  sandy  loam  on  sand 

60.4. ..  .Brown  sandy  loam  on  gravel 
60.5. ..  .Brown  sandy  loam  on  rock 

61 Mixed  sandy  loam 

62 Brown  fine  sandy  loam 

63 Light  brown  fine  sandy  loam 

64 Yellow  fine  sandy  loam 

65 Gray  fine  sandy  loam 

80 River  sand 

81 Dune  sand 

82 Beach  sand 

90 Gravelly  loam 

95 Gravel 

98 Mony  loam 

99 Rock  outcrop 


THK  FERTILITY  IN  ILLINOIS  SOILS.  259 


APPENDIX  B 

In  the  following  tables  are  recorded  in  detail  the  analyses  of 
individual  samples  of  soil,  including  surface,  subsurface,  and  sub- 
soil samples,  from  which  the  averages  given  in  Tables  3,  4,  and  5 
were  computed;  but  in  addition  to  the  constituents  mentioned  in 
the  tables  of  averages,  the  detailed  tabular  statements  show  the 
limestone,  present  or  required,  the  total  organic  carbon,  and  the 
acid-soluble  phosphorus  and  potassium. 

In  the  first  column  is  given  the  location  from  which  the  sample 
(or  set  of  samples)  was  taken.  Thus,  N.W.,  N.E.,  N.E.,  15,  2  N., 
i  E.  3rd  P.M.  is  the  commonly  accepted  method  for  expressing  the 
exact  location  of  the  northwest  quarter  (10  acres)  of  the  northeast 
quarter  (40  acres)  of  the  northeast  quarter  (160  acres)  of  Section 
15,  in  Township  2  north  of  the  base-line,  and  in  Range  i  east  of  the 
third  Principal  Meridian,  as  established  by  the  United  States  land 
survey. 

The  averages  for  the  Lower  Illinoisan  gray  silt  loam  prairie 
soil  (330),  as  given  in  Tables  3,  4,  and  5,  are  based  on  the  analyses 
of  57  different  samples  of  soil  collected  from  nine  different  counties ; 
and  for  the  Early  Wisconsin  brown  silt  loam  prairie  soil  (1126) 
analyses  of  90  different  samples  from  ten  counties  are  represented ; 
while  for  less  extensive  soil  types  smaller  numbers  of  samples  have 
been  analyzed.  It  is  believed  that  the  data  are  sufficient  to  show  to 
a  satisfactory  degree  both  the  average  composition  and  the  local 
variations  of  each  soil  type. 

In  the  third  column  is  given  the  laboratory  number  for  each  in- 
dividual sample  of  soil,  by  means  of  which  any  sample  whose  analy- 
sis is  reported  in  the  following  tables  can  be  identified  in  the  store 
room,  and,  if  desirable,  further  investigated,  unless  the  supply  has 
been  exhausted,  as  is  the  case  with  a  few  samples  among  the  early 
collections,  in  consequence  of  which  some  determinations  are 
lacking. 

All  results  are  reported  on  the  acre  basis,  2  million  pounds  be- 
ing used  for  the  surface  soil,  o  to  7  inches  (or  more  exactly  o  to 
6^3  inches)  in  depth,  4  million  pounds  for  the  subsurface  soil,  7  to 
20  inches  (or  6%  to  20)  beneath  the  surface,  and  6  million  pounds 
for  the  subsoil,  20  to  40  inches  deep,  except  that  2^,  5,  and  7^ 
million  pounds  are  used  for  sand  soil,  and  i,  2,  and  3  million  pounds 
for  peat  soil,  because  of  their  respective  specific  gravities. 

By  this  means  the  results  given  are  not  only  easily  understood 
in  practical  application  and  readily  compared,  but  they  are  exact, 


260  BULLETIN  No.  123.  [February, 

being  based  only  upon  gravimetric  measurements  the  same  as  per- 
centages, to  which  they  may  be  readily  converted,  if  desired,  by  us- 
ing as  a  divisor  the  number  of  millions  of  pounds  mentioned,  and 
pointing  off  four  places.  Thus,  in  soil  No.  480  (first  line  in  the 
following  table)  the  3380  pounds  of  nitrogen,  800  pounds  of  phos- 
phorus, and  25,100  pounds  of  potassium,  in  2  million  pounds  of 
surface  soil,  may  be  expressed  as  .169  percent  of  nitrogen,  .040 
percent  of  phosphorus,  and  1.255  percent  of  potassium. 

In  the  column  headed  "Limestone  required"  is  given  the  number 
of  pounds  per  acre  of  limestone  (calcium  carbonate)  required  to 
correct  the  soil  acidity  of  the  stratum  named.  The  recommenda- 
tions concerning  limestone  in  Table  3  are  based  upon  the  average 
requirement  to  a  depth  of  20  inches  and  upon  average  results  from 
field  experiments. 

The  "Limestone  present"  is  computed  as  calcium  carbonate  from 
the  inorganic  carbon  found  by  liberating  carbon  dioxid  from  the  soil 
with  hydrochloric  acid.  For  normal  soils  and  for  practical  use  this 
is  believed  to  be  of  greater  value  than  any  other  form  of  expression. 
In  alkali  soils,  or  others  when  of  sufficient  importance,  all  carbon- 
ates should  be  reported  separately. 

"Organic  carbon"  is  accurately  determined  and  reported  as  such, 
instead  of  attempting  to  determine  or  to  report  "organic  matter," 
"volatile  matter,"  or  "loss  on  ignition."  It  may  be  assumed  for 
rough  estimation  that  organic  matter  is  one-half  carbon.  In  other 
words,  the  number  of  tons  per  acre  of  organic  matter  may  be 
roughly  indicated  by  pointing  off  three  places  in  the  number  of 
pounds  of  organic  carbon  reported. 

On  this  basis  soil  No.  684,  of  the  Late  Wisconsin  black  clay 
loam  in  DuPage  county  contains  116.6  tons  of  organic  matter,  and 
soil  No.  474,  of  the  unglaciated  yellow  silt  loam  in  Johnson  county, 
contains  17.6  tons  of  organic  matter,  per  acre  in  the  surface  soil. 
The  percentage  of  carbon  increases  with  the  age  and  decay  of  or- 
ganic matter.  Thus,  fiber,  or  cellulose,  contains  44  percent  of  car- 
bon, while  humic  acid  contains  nearly  60  percent. 

As  an  average  strong  hydrochloric  acid  (official  method  A.O. 
A.C.)  dissolves  85  percent  of  the  total  phosphorus,  but  only  25  per- 
cent of  the  total  potassium,  with  large  variations,  however,  in  each 
case.  It  is  perhaps  noteworthy  that  the  older  gray  silt  loam  prairie 
soil  of  southern  Illinois  is  not  only  lower  in  total  potassium  content, 
but  that  a  smaller  percentage  of  the  total  is  soluble  in  acid  than  in 
case  of  the  later  brown  silt  loam  or  black  clay  loam  prairies,  general 
averages  being  considered  in  each  case. 


1908.}  THE  FERTILITY  IN  ILLINOIS  SOILS.  261 

In  the  last  column  are  recorded  the  strata  sampled.  Each  soil 
sample  analyzed  is  a  composite  sample  composed  of  six  to  ten  rep- 
resentative borings  from  as  many  different  places  where  the  soil 
appears  to  be  typical.  The  depth  of  sampling  for  the  surface  is  de- 
signed to  be  the  depth  of  the  plowed  soil,  but  we  have  come  to  adopt 
7  inches  (or  6%  inches  of  well  settled  soil)  as  a  standard  for  that 
stratum.  Between  the  subsurface  and  subsoil  we  try  to  divide  on 
the  subsoil  line,  commonly  found  near  20  inches  in  our  most  exten- 
sive soil  types,  and  we  sometimes  discard  an  inch  or  two  at  the 
subsoil  line  in  order  to  secure  subsurface  and  subsoil  separately  and 
not  a  mixture  of  the  two.  Where  there  is  no  fairly  distinct  line  of 
division  we  make  the  separation  at  20  inches.  The  subsoil  is 
sampled  to  a  depth  of  40  inches,  which  is  about  i  meter,  a  depth 
frequently  used  in  other  countries. 

In  conclusion,  attention  is  called  to  the  fact  that  in  many  re- 
spects there  are  fairly  uniform  and  characteristic  chemical  distinc- 
tions between  the  most  important  and  extensive  soil  types,  aside 
from  the  most  marked  and  regular  differences  between  extreme 
types  (as  sand  and  peat).  Thus,  with  all  the  natural  variations  in 
nitrogen  and  phosphorus,  the  highest  figures  for  the  southern  Illi- 
nois gray  silt  loam  prairie  rarely  equal  the  lowest  for  the  brown  silt 
loams  of  the  corn  belt;  while  the  highest  figures  for  the  brown 
silt  loams  rarely  equal  the  lowest  for  the  black  clay  loams  in  the 
same  areas.  Soil  acidity,  or  requirement  of  limestone,  may  be  as 
constant  a  characteristic  for  one  soil  or  subsoil,  as  the  presence  of 
limestone  is  for  another.  On  the  other  hand,  it  must  be  borne  in 
mind  that  variation  and  gradation  is  the  universal  law  of  nature,  ap- 
plying to  soils  even  more  strongly  perhaps  than  to  rocks,  plants,  and 
animals;  and  yet  soils  can  be  surveyed,  mapped,  and  classified  or 
graded,  physically,  chemically,  and  agriculturally,  as  well  as  apples, 
corn,  or  cattle,  all  of  which  are  commonly  marketed  by  grades  or 
classes. 


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